Implements undo/redo for both properties and filters. Works by creating
a new callback that gets called to save undo/redo states after a timer
is fired. Also disabled undo/redo until the actions have completed to
prevent a user from being able to disrupt the stack by perfoming actions
before others have finished.
Code submissions have continually suffered from formatting
inconsistencies that constantly have to be addressed. Using
clang-format simplifies this by making code formatting more consistent,
and allows automation of the code formatting so that maintainers can
focus more on the code itself instead of code formatting.
This commit adds a preview to the properties window for transitions.
The preview will play back the transition at the global transition
duration or the transitions fixed duration, between two private scenes
with an A and B label, and different background colors.
