Expedite foreground promotion

[davidgyoung]

This moves the BeaconService call to promote itself to a foreground service to the first line in onCreate. This is done in an attempt to avoid crashes initiated by Android caused by the failure to promote a service to a foreground service within 5 seconds. Such an exception looks like this:

android.app.RemoteServiceException: Context.startForegroundService() did not then call Service.startForeground(): ServiceRecord{2ce3f6e u0 com.myapp/org.altbeacon.beacon.service.BeaconService}
    at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1801)
    at android.os.Handler.dispatchMessage(Handler.java:106)
    at android.os.Looper.loop(Looper.java:210)
    at android.app.ActivityThread.main(ActivityThread.java:7124)
    at java.lang.reflect.Method.invoke(Method.java)
    at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:493)
    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:898)

Because the service is started on the main thread, it is possible that if that thread is very busy or blocked (potentially by other apps!) then it may take a long time to even call this onCreate method. In some cases where the main thread is busy or blocked, it may not be possible to do this in 5 seconds. Forum posts are full of claims from crash logs that this happens sometimes.

This is no guaranteed fix. But moving this to the top of the method gives the best thing that this library can do to prevent this crash. The app developer needs to take care not to initialize this library to start scanning in a case where the main thread could be blocked or overly busy. In other words, don't initialize beacon scanning then immediately do a large amount of work on the main thread.

This is in the 2.19-beta version of the library