Calibrate buttons, heading weights

Brought back the dual calibrate buttons (most of the time I only care
about the compass)
The heading weight gets applied to the training data AFTER loading it
Stop the updating thread when switching activities
Logging disables
Merge branch 'master' of https://github.com/mastergberry/SmartRover
Bit of A* cleanup, initial position, heading weight

Cleaned up some A* stuff, especially in converted feet to tiles
Bug in saving the heading
You can now specify an initial position to PositionManager