add orientation sensor
enable Orientation sensor by default
Merge branch 'master' into orientation

Conflicts:
	src/java/com/github/ruleant/getback_gps/lib/GeoOrientation.java
select default sensor based on preference to choose orientation sensor
preferences is stored as string
fix coding style
Current bearing is not updated when using sensors, close #148
move microsecond conversion to Tools class
Merge branch 'orientation'
add automatic option
calibrate sensor based orientation with location based orientation on location update, issue #137
use constant, issue #137
reset bearing offset when required circumstances are not fulfilled, issue #137