Add little more logic for paid courses

LMS-2510

* Don't show sidebar if only one language is present
* only add in the default language code if it's not already present

Also, refactor tests such that we're not deleting users or prefs

LMS-2156

Added a banner that students can use to dismiss the "you have failed reverification" message.  Also, removed unused code, wired up the sidebar for design

Also, removed an unused template

Added verification sidebar, banner for major courseware sections, quality & test improvements

Quick-and-dirty end-to-end flow, functional for at least the case of one course in need of re-verification.

Ready for design to start taking a look; still needs tests and code cleanup

Bug: LMS-1603

Also includes some tests

Story: LMS-1127