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
