localize the course home page

fixes CNVS-2607

test plan:
 - set the language for a course to something other than English
 - view the course home page
 - that language should be used
 - other courses' home pages/other pages should be unaffected

Change-Id: Ibee1b22003871ff942ad2f46e98073f12c449377
Reviewed-on: https://gerrit.instructure.com/29617
Tested-by: Jenkins <jenkins@instructure.com>
QA-Review: Nathan Rogowski <nathan@instructure.com>
Reviewed-by: Jeremy Stanley <jeremy@instructure.com>
Product-Review: Jeremy Stanley <jeremy@instructure.com>