Consolidate different ways to close the app

[GoogleCodeExporter]

I've noticed the programs behaves in different ways depending how you quit. 
This used to happen even with previous versions and before the "mac dedicated" 
version.
1) If you quit by closing the program window (clicking on the X box), it asks 
you if you want to save the unsaved changes before quitting. When you open the 
program again everything goes smooth.
2) If you quit from the File menu (File -> Exit), it asks you if you want to 
save the unsaved changes before quitting. When you open the program again there 
is an Auto-save message telling you that the application wasn't closed normally 
in the previous session and asking you if you want to open the last auto-saved 
file.
3) If you quit using Cmd+Q (the equivalent to Windows' ALT+F4) the program 
quits abruptly without asking you if you want to save the unsaved changes and 
when you open it again there is an Auto-save message telling you that the 
application wasn't closed normally in the previous session and asking you if 
you want to open the last auto-saved file.
I don't know if the same thing happens on the other operating systems.

Original issue reported on code.google.com by bancika@gmail.com on 8 Oct 2012 at 10:30