Add method to retrieve receiver battery level
Added icons on the top to indicate RSSI, receiver battery, and an indicator to tell the user when there is more than a 20 minute difference between the receiver display time and the uploader time
Merge remote-tracking branch 'origin/wip/cookie' into wip/cookie
Merge remote-tracking branch 'origin/wip/cookie' into wip/cookie

Conflicts:
	app/src/main/java/com/nightscout/android/MainActivity.java
	app/src/main/java/com/nightscout/android/dexcom/SyncingService.java
Merge remote-tracking branch 'origin/wip/cookie' into wip/cookie

Conflicts:
	app/src/main/java/com/nightscout/android/MainActivity.java
	app/src/main/java/com/nightscout/android/dexcom/SyncingService.java