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().
The RPC calls the daemon executable uses to talk to the running daemon
instance have mostly been added back in. Rate limiting has not been
added in upstream, but is on its way in a separate effort, so those
calls are still NOPed out.
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.
