Adding Brain Wallet Generator API

Generates a brain wallet plus salt to facilitate more robust backups
and recovery.
Adding an index of address to transaction

This is meant to facilitate light weight wallets.
Don't make UIAs retractable by default; resolves #1114
Merge branch 'develop' into bitshares

Conflicts:
	libraries/blockchain/market_operations.cpp
Merge branch 'bitshares' of github.com:BitShares/bitshares into bitshares