No real changes.
Added a line to add the pre-edited command components into a stack inside the UndoRedoProcessor class.

Added a new method called markAsIncomplete for use inside the UndoRedoProcessor
Added a line for the undo method
New class called UndoRedoProcessor for the project to handle Undo and Redo commands. Need Yui Wei to handle the commands for it.
Added a setter method to set the task as incomplete.
Added lines to add commands to the UndoCommand stack inside the UndoRedoProcessor class.