Improve support for custom and built-in actions

[soumya92]

• Added support for app-provided custom actions as a third pane in the controller activity. Displays the app-provided name, icon, and description, and executes the actions on tap.
• Changed shuffleMode from a toggle to mode-cycling and display the current shuffle mode. Also added a similar mode-cycling view for repeatMode.
• Replaced the thumbs up/thumbs down actions with a fully-fledged control that can display thumbs up/thumbs down, heart, stars, or even percentages, based on what the MediaController specifies as the rating style.

[soumya92]

cc @rasekh