Add hooks and classes, initially to support GuidedTour

* Hooks for activation, deactivation, save dialog state change,
  and tab setup.
* Class for save button (needed to point to it in a clean way).
  Also done for cancel button to be consistent, though GuidedTour
  doesn't currently use this.

Change-Id: I4a0e0631d513fb09c3408f2f36a0de0bd51e1a37
Merge "Add hooks and classes, initially to support GuidedTour"