had to fix a couple of small bugs, but the blockchain is downloading
into the new database now.
will be testing it further.
For now it is just the core consensus required databases:
* block indexed by height/hash
* spend indexed by output
* tx indexed by hash
Once I'm confident of their operation, I'll begin adding in the others.
One new feature is that 'optional' databases will be able to be
activated as needed from a certain block height. i.e to avoid indexing
history for the whole blockchain if it doesn't interest you.