* Make mempool aware of MaxGas requirement
* update spec
* Add tests
* Switch GasWanted from kv store to persistent kv store
* Fix typo in test name
* switch back to using kvstore, not persistent kv store
* better overview section
* section on tags
* remove notes about state/concurrency from CheckTx
* incorporate feedback from #2249
* explain how validator set updates effect future blocks
* addr_book_strick=false on local nets
* link to spec
* spec: remove TODO, see #1749 instead
* spec: make issues from TODOs
* update docs on addr_book_strict option
* mempool: Store txs by hash inside of cache
This allows for large cachesizes, without fear of the memory
consumption growing rapidly.
* (squash this) rename hashedTx -> txHash
* crypto/secp256k1: Fix signature malleability, adopt more efficient encoding
This removes signature malleability per ADR 14, and makes secp match
the encoding in ADR 15.
* (squash this) add lock
* [p2p/pex] connect to more than 10 peers
also, remove DefaultMinNumOutboundPeers because a) I am not sure it's
needed b) it's super confusing
look closely
```
maxPeers := sw.config.MaxNumPeers - DefaultMinNumOutboundPeers
if maxPeers <= sw.peers.Size() {
sw.Logger.Info("Ignoring inbound connection: already have enough peers", "address", inConn.RemoteAddr().String(), "numPeers", sw.peers.Size(), "max", maxPeers)
```
we print maxPeers = config.MaxPeers - DefaultMinNumOutboundPeers. So we
may not have enough peers even though we say we have enough.
Refs #2130
* update spec
* replace MaxNumPeers with MaxNumInboundPeers/MaxNumOutboundPeers
Refs #2130
* update changelog
* make max rpc conns formula visible to users
* update spec
* docs: note max outbound peers excludes persistent