[LMS-2757]

This will be used to detect courses that are linking to Stack Exchange
sites so we can handle them specially when generating data dumps.

This commit adds the non-courseware lms/djangoapps and lms/lib.

These keys are now objects with a limited interface, and the particular
internal representation is managed by the data storage layer (the
modulestore).

For the LMS, there should be no outward-facing changes to the system.
The keys are, for now, a change to internal representation only. For
Studio, the new serialized form of the keys is used in urls, to allow
for further migration in the future.

Co-Author: Andy Armstrong <andya@edx.org>
Co-Author: Christina Roberts <christina@edx.org>
Co-Author: David Baumgold <db@edx.org>
Co-Author: Diana Huang <dkh@edx.org>
Co-Author: Don Mitchell <dmitchell@edx.org>
Co-Author: Julia Hansbrough <julia@edx.org>
Co-Author: Nimisha Asthagiri <nasthagiri@edx.org>
Co-Author: Sarina Canelake <sarina@edx.org>

[LMS-2370]

STUD-1140

If this management command fails it's tough to figure out why without
seeing the text from the exception.  Luckily comment service does
return useful feedback, we just have to show it.  This one-line
change just add the exception text to the error message.

Before (with spurrious debug msgs removed):

    sefk@util1:~$ ./manage.sh reload_forum_users Anthonyhubendurance
    update user info to discussion failed for user with id: Anthonyhubendurance

After:

    sefk@util1:~$ ./manage.sh reload_forum_users Anthonyhubendurance
    update user info to discussion failed for user with id: Anthonyhubendurance, error=u'["Email is already taken"]'

No unit testing (sorry) added since this doesn't have coverage
already, and it's just a simple error case.

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.