Settings: Do not disturb automatic rule updates.

 - Remove FAB for adding rules, move to last preference.
 - Add first-class event condition type and config sub-page.
 - Always show radio buttons when adding rules.
 - Add new data model for event rules.
 - Add stub condition provider for event rules (always false for now).
 - Add rule-type icons to rule preference rows.

Bug: 20064962
Change-Id: Id5acde371eb2e7d22b1f195459897614db5ba80a