fix #249: report battery levels even if no GPS lock

@professr I noticed you added a "newStatus" observable to the GPS class.
Do you remember why you didn't remove the old GPS status (which seemed
to be dumber).  Is it just because you didn't want to risk breaking
MeshService?  (I assume) In this change I removed the old Observable
and all seems well (just using newStatus everywhere).

src/gps/GPS.h

@@ -25,7 +25,7 @@ void readFromRTC();
  *
  * When new data is available it will notify observers.
  */
-class GPS : public Observable<void *>
+class GPS
 {
   protected:
     bool hasValidLocation = false; // default to false, until we complete our first read
@@ -48,6 +48,7 @@ class GPS : public Observable<void *>
 
     virtual ~GPS() {}
 
+    /** We will notify this observable anytime GPS state has changed meaningfully */
     Observable<const meshtastic::GPSStatus *> newStatus;
 
     /**