Fix back and cancel flows

This fixes all the back flows (finishing activities when they are not
needed). Also fix some transition animations.

Add a toast when "See other apps" is selected with changes done. This
will appear even if something is changed and reverted, as that kind of
thing is not tracked.

Test: manual, go over flows
Fixes: 154741024

Change-Id: I24611f4f32e41c7dd3774620518f2945db081727