Added JAVA generator

This PR adds the JAVA MAVLink generator originally written for [DroidPlanner](https://github.com/DroidPlanner/droidplanner).

The changes from #228 are changing the name of the commit-er, and adding Java to the travis-ci build.
This needs to be fixed - it has to refer to the dialect (common, pixhawk or ardupilotmega) the tool is generating.