Allow location url_names to contain ':', mapping to / on file load

Fix latent bug in access checks in get_module

Eagerly load modulestores on server startup

Fix bug with sorting discussion forums 

Feature/rocha/wiki cheatsheet

* New format: {tag}://{org}/{course}/{category}/{name}[@{revision}]
* Updated tests, code
* Added test chapter with : in url_name in toy course
* added test html page with : in url_name
* added a note to docs

Feature/victor/unique names

add manage_course_groups command to lms_migration

* All access checks now done for the "user" param, ignoring request.user
  - This matters for xqueue callbacks and for instructor view of student progress
* An effect of this change is that if a student couldn't see their own 'progress' tab,
  the course instructor won't be able to see it either

fixed a tiny bug that loading icon sometimes doesn't appear at the right place / doesn't go away

Switch django-wiki dependency to a clone in our org

Set request.user = student when impersonating a student

Important fix! Remove HTML tags from Markdown code.

Do URL replacement in course info page

Added a log in button to the courseware when unauthenticated

- only relevant in tests due to start dates
- still irritatingly intricate logic...

* currently only in the staff view of student progress page

[Fix #34379687]

empty default for comments_service_key and comments_url because it was b...

empty default for comments_service_key and comments_url because it was breaking configs that do not have it in env.json

Added SECURE_PROXY_SSL_HEADER to env/aws. Re-enabled wiki directories

Fixed WikiPath regexp.

fix inline discussion