add orientation sensor
enable Orientation sensor by default
use Preference to enable sensor based updates of current bearing, close #131
Merge branch 'test_travis'
mention move of isTimestampRecent() to Tools class [skip ci]
update Travis build badge to svg [skip ci]
install python-matplotlib dependency to generate buildtime trend graph
add preference to choose orientation sensor
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install buildtime-trend dependencies using pip
remove timestamp
add timestamp for installing python dependencies
disable optimisation for python compilation
sudo is required to install pip dependencies
remove sourcegrpah badge [skip ci]
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Currently translated at 100.0% (70 of 70 strings)
use updated weblate badge [skip ci]
don't use https for weblate badge [skip ci]
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