(WIP) RTL

This PR sets up LMS and Studio to support RTL languages. Not every detail has been accounted for*, but every page should generally support layout from right to left. 

@talbs can you check the sass? 
@nedbat can you help with mako variables (and switching body classes) on the html templates - and review as you see necessary? 
@shnayder @sarina can you check from an LMS standpoint?
@cahrens can you review for Studio?

NB: This branch currently has come hardcoded values that need to be variable-ized before merging.

*Expanding arrows have not been rotated around, prev/next arrows have not been switched, and other small details I may not know need fixing may exist.
NIT: This file name (covering theming, css redundancy, RTL) is screaming that more effort is needed this layer of how styling is applied per application. No action needed for this PR, but adding a layer as part of this work is really pushing it.