Launch player activity as singleTop

Change the player activity launch mode from singleInstance to singleTop,
keeping it in the current task and allowing the back stack to be preserved.
This should fix this bug reported by m0d:

"I just noticed that if you download a module and play it, leave the app
 and go do something else in another app, when returning to xmp via the
 notification panel, you cannot go any further back in the screens to get
 back to the main screen. (or at least I haven't found a way yet).

 Instead tapping the notification takes you to the play screen of the
 currently playing module, hitting the back button exits the notification
 completely. Seems unintuitive, perhaps could you add another button to
 enable the possibility of going back to the main screen to download another
 module?"

Signed-off-by: Claudio Matsuoka <cmatsuoka@gmail.com>
Cosmetic changes in XmpApplication

Signed-off-by: Claudio Matsuoka <cmatsuoka@gmail.com>
Service notification code cleanup

Signed-off-by: Claudio Matsuoka <cmatsuoka@gmail.com>
Silence bogus PMD warnings

Signed-off-by: Claudio Matsuoka <cmatsuoka@gmail.com>