RTL (right-to-left) language support.

[Christopher Allan Webber]

We need RTL (right-to-left) language support in MediaGoblin.

Presumably this requires:


-  Pushing a variable into the general template context specifying
   whether the current language is LTR or RTL
-  Making an RTL stylesheet
-  ... other things?

I'm assigning Osama Khalid to this ticket. Osama, you don't have to
do this necessarily, but at least please give advice on what needs
to be done (you can unassign yourself then if you like).