Left TODO:

 * Change custom theme text to indicate what themes are being used.
   - requires breaking string freeze

 * Sanity check saving.  In particular, \n needs escaping.

 * Fix the collation of the Details dialog.  Seems to be going on theme
   name, not readable name.

 * When saving a theme that started as an initial custom theme, kill
   that from the list.

 * Have the 'set Background' button do something.

 * make sure that installing themes go to the right place.