Add colors to tiles

Protoype for modifying color of tiles. Provides 2 modes:
qs_color_enabled: allows changing background of tiles
qs_color_icon: allows changing color of icon (only use with
qs_color_enabled)

Enable using:
adb shell settings put system <name> <value>
where name is one of (qs_color_enabled|qs_color_icon) and value is (0|1)

With qs_color_enabled, color of individual tiles can be changed using
adb shell settings put system qs_color_enabled/<spec> <color>
where spec is as defined in QSFactoryImpl and color is one of
(red|green|blue|yellow|accent).

Test: manual

Change-Id: I66096cfa5cb8570074b1547ca3e41bd0888973fa