Work on “CLI” RPC client

* Move all methods into MastercoinCLIClient
* BitcoinCLIClient extends MastercoinCLIClient (for now)
* Minor API fixes/improvments
* Add more Documentation comments
Use MastcoinCLIClient in RegTestSendManySpec

* Set client = MastercoinCLIClient in BaseRegTestSpec
* Use lowercase method names in RegTestSendManySpec
Further cleanup of RegTestSendManySpec

* Add gettransaction() method to MastercoinCLIClient
* Consistent use of MasterCoinCLIClient
* Other minor cleanup
JavaDoc/GroovyDoc improvements