DB prototyped.
Build fix.
PoC-7: Reversion of 0-hashes, empty-list hashes and sha3('') -> ''
Merge branch 'develop' into mk_jsonrpc

Conflicts:
	alethzero/MainWin.cpp
	alethzero/MainWin.h
	libqethereum/QEthereum.cpp
	libqethereum/QEthereum.h
	third/MainWin.cpp
	third/MainWin.h
missing setDefaultBlock method
ldb access from api
whisper in web3jsonrpc