The body of the enrollment message template

Tokenize platform name in message.

Changing to a datetime enrollment approach

Adding sorting. A little refactoring.

Adding confguration model for time delta

Adding admin registration and basic form for new config model.

Fixing docstring typo

Updating default time delta to 0, adding test to show it disabled functionality.

Removing the form from configuration and tweaking the enrollment message html

This reverts commit 1955aade36675289bdbc01554b6f74242754a746.

Updating EX-60 logic

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