No Method to Undo/Redo Changes

[weibullguy]

Currently no method exists to undo and redo changes made to the RTK Program database. Please add this functionality. This will likely require the use of database transactions. Undo and redo level should be at least 25 and preferably will be user-selectable up to a maximum level.

[rakhimov]

Qt provides UndoStack/Command framework that nicely integrates with document modification detection. Just my :+1: for PyQt.