Settings: percentage text charging indicator and custom color (2/2)

Due some user complains cause of missing charging indicator on
battery percentage and percentage+icon in statusbar this commit
introduces two features

- percentage/percentage + icon color indicator on charging
  (default color = green)
- custom charging color for all battery symbols with percentage text
  (percentage/percentage+icon/circle with percentage/dotted circle with percentage

- a bit code cleanup

Patchset 2
- cleanup to reduce provider settings calls

Patchset 3+4
- cleanup + commit message

cheers

Change-Id: I9bba9a051f9623fb87e6cb95f5520f7eeb991c43