Template variable name change

I've recently installed `rosetta-grappelli` and discovered that it isn't working; specifically, the `pofile.html` template showed nothing. Looking through the rosetta code made it clear that the variable is now called `rosetta_messages` instead of just `messages` (although I have no idea when it was changed), so I made the change and am submitting it to you to incorporate it if wanted.

Best regards,

Berislav