i18n LMS and Studio components of course handouts

Tagging Kevin Luo from Stanford for the LMS part.

@andy-armstrong can you take a look at the Underscore file? I verified it on localhost.
I'm still slightly nervous about outputting translations directly into the HTML stream without escaping. It hasn't bitten us yet, but some day it could.

See the discussion here: https://github.com/edx/edx-platform/pull/4347#issuecomment-48477774