Features and fixes.

-----Fixes for Saving (Dirty Files)
Last Minute Check to make sure that when you close the app if you have dirty files, it asks if you want to save
If you have a dirty file and do open and hit no and cancel out of the new opening, you no longer lose your file
Dirty is caused whenever you change, add or remove data (this includes PolyPoints, folders, images, polygroups etc)

----PolyGroup throughout Frame change
When you select a polygroup (body/attack etc.) and then go to the next frame, your active poly group
will always be the same one as the previous Frame until you select another one

Added Hotkeys
Ctrl N -> New
Ctrl Q -> Close
Ctrl O -> open
Ctrl S - >Save
Ctrl + Shift S -> Save As
Ctrl E - >Export
(currently only works when you click on something outside of the image pane)