Add middleware optionally to catch unenrolled students who fail has_access (TNL-286)
redirect users from about page to info page when there is a marketing site (TNL-286)
display banner on course info page if user is not enrolled (TNL-286)

write failing tests for info page banner
only load tabs if user is enrolled in course (TNL-286)

add tests for static tabs
update number of queries in embargo test
Merge pull request #5281 from edx/adam/hide-tabs-if-not-enrolled-rebase-2

Deployed as hotfix
Merge remote-tracking branch 'edx/release'