Features coming down the pipe will want to be able to:
* Refer to enrollments before they are actually activated (approval step).
* See what courses a user used to be enrolled in for when they re-enroll in
  the same course, or a different run of that course.
* Have different "modes" of enrolling in a course, representing things like
  honor certificate enrollment, auditing (no certs), etc.

This change adds an is_active flag and mode (with default being "honor").
The commit is only as large as it is because many parts of the codebase were
manipulating enrollments by adding and removing CourseEnrollment objects
directly. It was necessary to create classmethods on CourseEnrollment to
encapsulate this functionality and then port everything over to using them.

The migration to add columns has been tested on a prod replica, and seems to be
fine for running on a live system with single digit millions of rows of
enrollments.

This reverts commit 2df3fe93.

Conflicts:
	common/static/coffee/src/discussion/utils.coffee

This reverts commit acfd0d9f, reversing
changes made to e4194c99.

move the provisioning seeding from LMS into Common. Add provisioning seeding calling from create new course view.

fix cohorts in create, and read, and update regular expressions to fix courses with periods not working in General commentable

loaded into the page in a data attribute instead of loaded on request via ajax.
The user profile page also does not provide facilities for adding
comments/responses, which I think would clutter the page too much.

Also removed some unused stuff from views.py.

course id for seed_permissions_roles, and also the script itself to tell you that.