LEARNER-1628

This allows enrolled users to write reviews on the reviews page that
can be accessed through the course tools sidebar. A button in the top
corner of the page toggles the widget that is configured with a
setting in the common.py file. The reviews tool is Course Talk.

Adding a reviews page to the course and updating the reviews module on the course about page. Removed the existing coursetalk implementation and put it in a fragment, removed the tests as well. Added configuration settings to specify the reviews template as well as the reviews provider. This is all protected by a waffle flag.

Store user's preference indefinitely.

This sock sits at the bottom of both the home and the course content pages. It allows the user to click a 'Learn More' button to open a panel that allows the user to navigate to the upgrade checkout page. The sock is only shown for users that have not yet upgraded in a course that has a verification upgrade date that has not yet passed. Python tests cover the various course mode and upgrade dates.

2) Updating the course experience sass file to use variables it can reference in the version two variable sass file.
3) Updating date styling on course home page as explained in LEARNER-1297.
4) Expanding side outline panel to take up a third and not a quarter of the content size.

LEARNER-1112

Fix for LEARNER-859: Updating styling on the course updates page to more clearly differentiate between multiple updates. Specifically:
- Updated styling on date in the top left corner
- Added horizontal line between updates
- Removed ability to toggle updates on and off
- Cleaned up code to always show all updates:

LEARNER-879

Also add it to the course home page.

LEARNER-27

LEARNER-607

LEARNER-39

LEARNER-39