Improved max run time accuracy.

Added a notification icon when tracker is running.

Keep "stopped on" time in prefs in case the app is killed by the OS.
Added a "tracker=start" / "tracker=stop" http request on start/stop.
Prevent a burst in onLocationChanged calls, which may happen sometimes.
Lowered max run time to 8 hours by default, to reduce battery drain.
=> v 1.1

Simplified code using IntentService instead of Service.

=> version 1.0.1

Modified .gitignore