All of the functionality for the LMDB implementation of BlockchainDB is
implemented, but only what is in tests/unit_tests/BlockchainDB.cpp has
been tested. This is basically add a block, see if you can get the
block and a tx from the block. More tests should be added at some
point.
Still needs testing (and need to write a few more unit tests), but
everything should be there. Lots of unfortunate duplication,
but...well, I can't see a way around it using LMDB.
A couple of other minor changes in this commit, only slightly relevant.
