Added course level lang attribute for LMS
added lang attribute to Studio
fixed error when trying to get language attribute on course that does not exist
simplified code
added lang attribure to more places in LMS, added migration for language attribute in course_overview
fixing contraints in the database for language attribute
added lang attribute to several more places in LMS and Studio
added lang attribute to discussion and custom pages; cleaned up code
fixed issue that was causing test failures
moved lang attribute higher in tree in two places
eafb79defc