Most of #98 (action bar improvements).

Icons are the ones from https://developer.android.com/design/downloads/index.html which says "You may use these materials without restriction to facilitate your app design and implementation."

Remaining work is:

 * Draw the ic_action_game and ic_action_type that I sketched on the issue.

 * Fix the action bar flags resetting logic in onConfigurationChanged.

 * As part of that, make the title disappear when undo/redo are in action bar and the screen is narrow.

 * Apply changes to whether undo/redo are in action bar without a restart.

 * Give the "completed" popup darker buttons or darker versions of the icons, as it's white on grey right now.