Added getTask in IDonStorage (please change as appropriate Yifei)
Added findTask by ID and deleteTask by ID with corresponding message string constants.
Changed parameters of a few IDonStorage methods to reflect the discussion on 19/09/2014.
Added initialize method to IDonLogic.
Added Cloneable interface to IDonTask for use with the undo command.
Implemented the clone method in DonTask.
Added a few more enums to ResponseType.
Applied formatting to IDonResponse.
Added editTask method to DonLogic.
Added undoLastAction method to DonLogic. Everything up to this point is untested just FYI.
Added DonAction private class in DonLogic to encapsulate an action performed within DonLogic due to user input. For use with the undo command.
The createTask, editTask and deleteTask methods that have been implemented now add to the action history so that they can be undone.