More sorting options in "Edit Deck" window (e.g. sort by number of lapses, difficulty, etc)

Currently, the Edit Deck window allows sorting by Question text, Answer text, and Category. I think it would be useful to allow other types of sorting options. Every item in the Card Statistics menu for an individual card (difficulty, days since last repetition, etc) is something numerically quantifiable and meaningful, so enabling the user to sort by those criteria could enhance the usefulness of the program as a whole.

To give a concrete example, I would love to be able to sort by difficulty so that I could periodically (once per month or so) check to see which cards I am having the most trouble with so that I can spend time rephrasing or altering the contents of those cards to make them more memorable.

These extra sorting options could be implemented as options in a drop-down menu reached by right-clicking on the sorting bar.