migration towards new style history which consumes less data and is easier to index by block height.
Merge pull request #97 from evoskuil/develop

Replace big_number with generated code, add code generator.
no more stop index value in blockchain::fetch_history()
remove blockchain:: qualifier (obsolete) in docstring api info.
removed mmfile to be moved to libbitcoin-blockchain.
renamed history_row_id to point_ident
update checkpoint.
move stealth struct out of blockchain class so blockchain:: qualifier isn't needed.
Merge branch 'develop' into version2

Conflicts:
	include/bitcoin/bitcoin/blockchain.hpp
	include/bitcoin/bitcoin/format.hpp
	include/bitcoin/bitcoin/utility/mmfile.hpp
	src/blockchain.cpp
	src/transaction_indexer.cpp
	src/validate.cpp