Everything except actually *using* BlockchainBDB is wired up, but the db
itself is not yet working. Some error about user mem not large enough.
I think I know what this error means, but I can't determine the cause.
Notes: BerkeleyDB does not allow 0-indexing in its recno type databases,
so block numbers *in the database* will be 1-indexed. Modifications
to indexing have been made as needed.
LMDB implementation code copy/paste/modified into the Berkeley DB
implementation. Need to test if it builds, then if it works, and so on,
but the code is all there.
