Switched to codeload + other adjustments.

Signed-off-by: Rosen Penev <rosenp@gmail.com>

fix Makefile chmod (644)
replace MD5SUM with HASH
add PKG_MIRROR_HASH when PKG_SOURCE_PROTO:=git

(PKG_SOURCE_PROTO:=svn tarballs are not reproducible for now)

Signed-off-by: Etienne Champetier <champetier.etienne@gmail.com>

keplerproject.org has been long gone.

Signed-off-by: Karl Palsson <karlp@etactica.com>

Signed-off-by: Dirk Chang <dirk@kooiot.com>