Elegant rtl/ltr css switch, LMS RTL fixes, language aware @cache_if_anonymous

.gitignore

cms/static/sass/style-xmodule.scss

...on/djangoapps/pipeline_mako/templates/static_content.html

common/djangoapps/util/cache.py

lms/static/sass/application-extend1-rtl.scss

lms/static/sass/application-extend2-rtl.scss

lms/static/sass/application-rtl.scss

lms/static/sass/course-rtl.scss

lms/static/sass/course/layout/_courseware_header.scss

lms/static/sass/discussion/_discussion.scss

lms/static/sass/multicourse/_dashboard.scss

lms/static/sass/shared/_header.scss

lms/templates/main.html