Add tests against the Bitcoin Regtest

[ceyhunsen]

There should be tests that compares mock RPC with the real Bitcoin RPC (regtest). These tests are qualified as "system" tests and probably won't end up in rust code. Can be shell or other kind of scripts.

Bitcoin repository's tests should be checked if any of the existing tests can be used.

This issue is very important because it will be the most trust worthy way to show that mock RPC really works as the real thing.