Start a test blockchain for unit/integration testing

[jbax]

Would be great to be able to start a local blockchain for test purposes. Not sure how easy or hard that would be. But the goal is to enable unit or integration tests to run against with a few "real" wallets with some funds available on this test blockchain. If possible everything will run locally. The closer it can get to how in-memory databases work, the better (setup itself automatically, run tests, destroy itself, recreate everything again, run other tests, destroy again, and so on)