Clean up testing code, fix false negatives

* Create ConsensusComparison class to centralize some checks

* Specifically, fix an error with the use of Map.intersect() method that
  was filtering out balances that didn’t match before comparing them.

* Create and use CurrencyID.MSC_VALUE constant

* Create experimental Java types for CurrencyID and Ecosystem

* Create a few Spock Unit tests (true unit tests, not integration tests)