stealth_database using new primitives.
stealth_db tool.
actually index stealth info.
fetch_stealth hook.
Merge branch 'master' into version2

Conflicts:
	include/bitcoin/blockchain.hpp
re-add initialize_blockchain() (used by unit test)
no need for conditional platform include. removed it.
remove block_header_database from Makefile.am (obsolete file)
add fsizes.hpp include to blockchain.hpp
don't forget to touch stealth files in db_paths.
fullnode has been ported over to libbitcoin-node