Migrate to regtest

[vnprc]

We need to get off testnet4 before we can start developing ehash redemptions because we need to control block production in order to get some mining rewards to distribute.

Update the bitcoind process and add a script to check the block height and mine 16 blocks on startup.

We should also have a just recipe to mine a new block.

[vnprc]

#52

[vnprc]

Oops! There was already an issue for this work. I didn't see it because it automatically closed when I merged the PR.

Nothing to see here. Move along. 😳