Synchronization now seems to work well even with the rapid fire
many inv-block messages that I'm seeing often on testnet3. I'm
not 100% sure measuring the len() of a buffered channel is safe
but it seems to work fine.
Got rid of 'sum' in the TxStore; can be computed from GetAllUtxos()
Might want to merge SCon and TxStore since there's not much going
on in TxStore any more...
pretty much everything is db based now. Still some concurrency issues
when multiple block inv messages come in (which they do) where
we used len(mBlockQueue) as a check for being synched up, which doesn't
quite work. Find a better way to do that...
Sync was non-deterministic because ingest was concurrent.
Now receiving tx messages is blocking, but that's OK, they really need
to be in the right order because the whole point of bitcoin is to put
txs in the right order. SendTx still has a problem that the change address
may not be recognized by ingest.
I'm getting away from having both in-ram and on-disk stores for the transaction store data.
it should all be on disk, it's safer that way. It might be slower but this will not
process many txs / second anyway.
when we get inv messages, txs are easy but blocks are a little tricky
block heigh synchronization is done via os' file system
signing is a bit inelegant (searches through inputs for pkscript matches)
but fast enough in practice
