Add warning that course teams can't see student-uploaded images
Merge pull request #572 from edx/sylvia/docs/DOC-812

Add warning that course teams can't see student-uploaded images
Updated many blocktrans strings for i18n
Got The Translation Strings to Pass Testing! Huzzah for arbitrary namescoping!
Added in comments for "due in" strings
Merge branch 'grady/i18n-strings' into grady/i18n-template-debug