There will need to be some more refactoring for these changes to be
considered complete/correct, but for now it's working.
new daemon cli argument "--db-type", works for LMDB and BerkeleyDB.
A good deal of refactoring is also present in this commit, namely
Blockchain no longer instantiates BlockchainDB, but rather is passed a
pointer to an already-instantiated BlockchainDB on init().
many RPC functions added by the daemonize changes
(and related changes on the upstream dev branch that were not merged)
were commented out (apart from return). Other than that, this *should*
work...at any rate, it builds, and that's something.
