Bring support for multisig and multiple sources, destinations into develop

Also, use python-bitcoinlib in `get_tx_info_2()` to parse Bitcoin transactions. (#217)

These changes are only live on testnet, and the testnet DB must now start at block 
282000
 281000. (Use `--database-file=` so that this testnet DB can co-exist with one from `master`.
Under this new scheme, is there no more `OP_RETURN` encoding?