Droneapi for droidplanner

Hi Arthur,

Here is a PR which adds 'pretty good' support for the drone api (live flight tracking and tlog updates).  It is configure as off by default (and labeled as alpha).  If you could include this in a test build for the 3dr folks that would be awesome - but not really useful yet for general release.  Things that need to happen before general release:
* Allow automatic delayed uploads of tlogs
* Support the UDP uplink - not just TCP
* Change to production server
* Pull the jars from maven central rather than including binaries in the build.

I'll finish these remaining bits in a couple of weeks?  After there has been some test user feedback on the various GCSes.