Implement CLI-style clients for Bitcoin and Omni

[msgilligan]

The current Java clients for Bitcoin and Omni are very close in name and behavior to the direct RPCs, but their names are camel-case and because Java methods can't have optional parameters there are overloaded methods with fewer parameters.

OmniCLIClient.goovy is a starting point for this work. There is a placeholder class BitcoinCLIClient.groovy as well. The idea is to use Groovy's optional arguments capability to more closely resemble the RPC methods themselves.

One of the reasons for this implementation would be writing functional tests that are very readable by people familiar with the RPCs from Bitcoin and/or Omni documentation or from using the CLI command-line tools.