SlimActions: add new actions and cleanup

A bit cleanup.

As well add 4 actions:

- camera intent
- play/pause music
- next music track
- prev music track
- wake up device

As well check for system ready on the other audio actions which are already present.

ToDo: One of the rare classes which are very bad documented. We need to add code comments
ASAP

Change-Id: I73bcfb6c60454de4d8494dfd846deee770022335

Conflicts:
	core/java/com/android/internal/util/slim/ButtonsConstants.java
	core/java/com/android/internal/util/slim/SlimActions.java