Overwrite GCM receiver to permit custom package

In order to move the GCM intent service class into another package but
the default application package one has to extend the GCM broadcast
receiver class and overwrite the getGCMIntentServiceClassName method to
return the custom class with the full package identifier.

This commit does that and makes the needed changes to the Android
manifest file.

Signed-off-by: Konrad Reiche <konrad.reiche@gmail.com>
Add retry to the status task

I am not sure why, but sometimes after requesting the server status and
receiving a HTTP 200 OK, the response content is null nonetheless. For
the time being I have added an automatic retry of this task, even though
I am not sure, if this helps at all.

Signed-off-by: Konrad Reiche <konrad.reiche@gmail.com>
Return class name dynamically

Instead of hard coding the class name as a string I am using the class
itself to return the name. This way it is more robust against changes
due to refactoring, even though that does not help on the level of the
Android manifest file.

Signed-off-by: Konrad Reiche <konrad.reiche@gmail.com>
Reinstate model and controller in onCreate

Sometimes I get the error, that the inbox handler is sending messages to
a handler on a dead thread. I can only imagine, that the previous thread
is abandoned, but its reference is kept. I am still unsure how one has
to handle this properly. For now I am reinstating the model and
controller everytime at the top of onCreate.

Signed-off-by: Konrad Reiche <konrad.reiche@gmail.com>