* Initial commit for 3181..still early

* unit test updates

* unit test updates

* fix check of dups accross updates and deletes

* simplify the processChange() func

* added overflow check utest

* Added checks for empty valset, new utest

* deepcopy changes in processUpdate()

* moved to new API, fixed tests

* test cleanup

* address review comments

* make sure votePower > 0

* gofmt fixes

* handle duplicates and invalid values

* more work on tests, review comments

* Renamed and explained K

* make TestVal private

* split verifyUpdatesAndComputeNewPriorities.., added check for deletes

* return error if validator set is empty after processing changes

* address review comments

* lint err

* Fixed the total voting power and added comments

* fix lint

* fix lint

* types: memoize height/round in commit instead of first vote

* types: commit.ValidateBasic in VerifyCommit

* types: new CommitSig alias for Vote

In preparation for reducing the redundancy in Commits, we introduce the
CommitSig as an alias for Vote. This is non-breaking on the protocol,
and minor breaking on the Go API, as Commit now contains a list of
CommitSig instead of Vote.

* remove dependence on ToVote

* update some comments

* fix tests

* fix tests

* fixes from review

* base verifier: bc->bv and check chainid

* improve some comments

* comments in dynamic verifier

* fix comment in doc about BaseVerifier

It requires the validator set to perfectly match.

* failing test for #2862

* move errTooMuchChange to types. fixes #2862

* changelog, comments

* ic -> dv

* update comment, link to issue

* more proposer priority tests

 - test that we don't reset to zero when updating / adding
 - test that same power validators alternate

* add another test to track / simulate similar behaviour as in #2960

* address some of Chris' review comments

* address some more of Chris' review comments

* temporarily pushing branch with the following changes:
The total power might change if:
   - a validator is added
   - a validator is removed
   - a validator is updated

Decrement the accums (of all validators) directly after any of these events
(by the inverse of the change)

* Fix 2960 by re-normalizing / scaling priorities to be in bounds of total
power, additionally:

 - remove heap where it doesn't make sense
 - avg. only at the end of IncrementProposerPriority instead of each
   iteration
 - update (and slightly improve)
   TestAveragingInIncrementProposerPriorityWithVotingPower to reflect
   above changes

* Fix 2960 by re-normalizing / scaling priorities to be in bounds of total
power, additionally:

 - remove heap where it doesn't make sense
 - avg. only at the end of IncrementProposerPriority instead of each
   iteration
 - update (and slightly improve)
   TestAveragingInIncrementProposerPriorityWithVotingPower to reflect
   above changes

* fix tests

* add comment

* update changelog pending & some minor changes

* comment about division will floor the result & fix typo

* Update TestLargeGenesisValidator:
 - remove TODO and increase large genesis validator's voting power
accordingly

* move changelog entry to P2P Protocol

* Ceil instead of flooring when dividing & update test

* quickly fix failing TestProposerPriorityDoesNotGetResetToZero:

 - divide by Ceil((maxPriority - minPriority) / 2*totalVotingPower)

* fix typo: rename getValWitMostPriority -> getValWithMostPriority

* test proposer frequencies

* return absolute value for diff. keep testing

* use for loop for div

* cleanup, more tests

* spellcheck

* get rid of using floats: manually ceil where necessary

* Remove float, simplify, fix tests to match chris's proof (#3157)

* types: ValidatorSet.Update preserves ProposerPriority

This solves the other issue discovered as part of #2718,
where Accum (now called ProposerPriority) is reset to
0 every time a validator is updated.

* update changelog

* add test

* update comment

* Update types/validator_set_test.go

Co-Authored-By: ebuchman <ethan@coinculture.info>

- rename fields, methods, comments, tests

* set the accum of a new validator to (-total voting power):

- disincentivize validators to unbond, then rebon to reset their
negative Accum to zero

additional unrelated changes:
- do not capitalize error msgs
- fix typo

* review comments: (re)capitalize errors & delete obsolete comments

* More changes suggested by @melekes

* WIP: do not batch clip (#2809)

* substract avgAccum on each iteration

- temporarily skip test

* remove unused method safeMulClip / safeMul

* always substract the avg accum

 - temp. skip another test

* remove overflow / underflow tests & add tests for avgAccum:

- add test for computeAvgAccum
- as we substract the avgAccum now we will not trivially over/underflow

* address @cwgoes' comments

* shift by avg at the end of IncrementAccum

* Add comment to MaxTotalVotingPower

* Guard inputs to not exceed MaxTotalVotingPower

* Address review comments:

 - do not fetch current validator from set again
 - update error message

* Address a few review comments:

 - fix typo
 - extract variable

* address more review comments:

 - clarify 1.125*totalVotingPower == totalVotingPower + (totalVotingPower >> 3)

* review comments: panic instead of "clipping":

 - total voting power is guarded to not exceed MaxTotalVotingPower ->
 panic if this invariant is violated

* fix failing test

* types: NewValidatorSet doesn't panic on empty valz list

* changelog

* WIP: switching to fixed offsets for SignBytes

* add version field to sign bytes and update order

* more comments on test-cases and add a tc with a chainID

* remove amino:"write_empty" tag

- it doesn't affect if default fixed size fields ((u)int64) are
written or not
- add comment about int->int64 casting

* update CHANGELOG_PENDING

* update documentation

* add back link to issue #1622 in documentation

* remove JSON tags and add (failing test-case)

* fix failing test

* update test-vectors due to added `Type` field

* change Type field from string to byte and add new type alias

- SignedMsgType replaces VoteTypePrevote, VoteTypePrecommit and adds new
ProposalType to separate votes from proposal when signed

- update test-vectors

* fix remains from rebasing

* use SignMessageType instead of byte everywhere

* fixes from review

* crypto/merkle: Remove byter in favor of plain byte slices

This PR is fully backwards compatible in terms of function output!
(The Go API differs though) The only test case changes was to refactor
it to be table driven.

* Update godocs per review comments

Currently the top level directory contains basically all of the code
for the crypto package. This PR moves the crypto code into submodules
in a similar manner to what `golang/x/crypto` does. This improves code
organization.

Ref discussion: https://github.com/tendermint/tendermint/pull/1966

Closes #1956

Refs #693

This reverts commit d02c5d1e30.

Also, fix consensus liveness issue.

This reverts commit 96a3502

Refs #581

an example of Search from godocs:

```
package main

import (
	"fmt"
	"sort"
)

func main() {
	a := []int{1, 3, 6, 10, 15, 21, 28, 36, 45, 55}
	x := 6

	i := sort.Search(len(a), func(i int) bool { return a[i] >= x })
	if i < len(a) && a[i] == x {
		fmt.Printf("found %d at index %d in %v\n", x, i, a)
	} else {
		fmt.Printf("%d not found in %v\n", x, a)
	}
}
```

* use increment and decrement operators.

* remove unnecessary else branches.

* fix package comment with leading space.

* fix receiver names.

* fix error strings.

* remove omittable code.

* remove redundant return statement.

* Revert changes (code is generated.)

* use cfg as receiver name for all config-related types.

* use lsi as the receiver name for the LastSignedInfo type.

In for loop of IncrementAccum(), Heap.Update() call is unnecessary when i == times - 1.

Refs #919

uint64 is considered dangerous. the details will follow in a blog post.