Removed convergence code as accelerometers are much more imprecise than the docs suggest.
This commit renames the DetectUnchangingLocation class to LocationChangeSensor.
* A subsequent commit will push the LegacyMotionSensor and significant motion detector code behind a common interface.

A ServiceLocator has been added to MainApp so that we can inject dependencies at runtime to aid in testing and decoupling interfaces.

Preliminary documentation is provided in docs/testing.md
Merge pull request #1338 from crankycoder/features/1294-rebased-sensor-tests

Features/1294 rebased sensor tests