All kinds of little foreground services fixes.

- Better explanations of some strings.
- Fix to use the right package when an item is pressed in
  the foreground services dialog.
- Improve java docs on Service.startForeground().

Bug: 37925387
    735566 lv - Android - [Source] Context unclear or missing:
    Apps running in background
Bug: 37925888
    735566 lv - Android - [Source] Context unclear or missing:
    Tap for details on battery and data usage
Bug: 37897953
    735566 gl - Android - [Source] Context unclear or missing:
    LEFT_SIDE, RIGHT_SIDE
Bug: 37943079
    Music is dying mid playback

Test: manual
Change-Id: Ied41932c61f59335bd18dfba3fcb13af28a0bddd