Add Control-Z / Undo functionality

[rpsforza]

No description provided.

[michaelgira23]

We could probably have a service, either add onto the whiteboard service or create another one, for querying all the markings, text, shapes, etc. from the database and creating a "queue" or "stack" of events that happened in sequential order in a specific whiteboard. This could help us when creating an undo/redo button.