Upgrade to 0.5.0-rc.2

- Add an assembly for building mapr
  (required to most easily make mysql driver available on class path)
- Updates the README
- Convert MyM3App to extend AbstractApplication instead of
  AbstractBuilder.
- Avoid NPE in MasterNode.stop
Merge pull request #7 from aledsage/upgrade/brooklyn-0.5.0-rc.2

Upgrade to 0.5.0-rc.2