Animation: Frame Change Notifications

This feature adds an optional canvas-notification for frame changes of different types. This was suggested by bollebib on phabricator as an improvement to his workflow with animation.

Default settings currently have frame change notifications only occur when navigating using QActions (for hotkey / button press events) which can help in circumstances where there's currently no Animation Docker or Timeline present. The main use for this feature is when in canvas-only mode where you might not be able to see any docker. It will also compliment the eventual scrub-wrapping feature requested by bollebib as well. An argument can be made this is really mostly necessary in canvas-only view where no timeline or animation docker is viewable, but since it's fully user configurable, we can continue to tweak the default settings until all users are happy.

Screenshot:

Here's the configuration window: