gh-159 Switch to SBT for better cross-compiled jar/module generation

* Package builds a jar and module.
* Cross compilation packaging generates modules for all Scala versions.
* copyMod task ported over to SBT.
* Added mod zip file as extra artifact generated which installs
locally via 'publishM2' task.
* Adjust release script to use SBT.
* Remove old gradle files.
Add ability to release of a different branch