Get GPS data from a single polled sentence

This simplifies things and makes it a lot easier to read the gps
module through a USB to ttl serial adapter.
Update unit tests

- Also eliminates errors in code exposed by the tests.
Merge branch 'features/gps-module'

As part of the merge, I removed the throws declaration from the GPS sensor
constructor - it doesn't look like it does throw any more.

Conflicts:
	project.latex.balloon/src/project/latex/balloon/BalloonController.java