Reapplies and revamps functionality on the assignment table.

* Reapplied the table data changes to also change to the mycourse object.
* Added in error checking for table changes.
* Added so the user can see Ghost Names (the psuedoname) of the students.
* Added tab functionality that Shade was wanting (Enter key will need to be looked at).
* Made it also so when using tab or enter actually makes the cell that the user is about to edit more focused.
* Also made it so "Back" button doesn't save the file, (it doesnt prompt the user just yet, we can work on that later), and have made it so you must select the Save menu item to save the current course to its proper xml file.