AwfulSemiModalViewController now sizes views that use auto layout.
Reimplement page settings as a semi-modal view controller.

* Theme picker now spans multiple rows, to ensure all theme buttons are visible.
* Add "Theme" label beside theme picker.
* Simplify theme picker button drawing, implementation, and creation.
* AwfulSemiModalViewController now has a theme as it subclasses
  AwfulViewController.
* Eliminate AwfulPageSettingsViewControllerDelegate.
Per documentation, override -sizeThatFits: instead of -sizeToFit.