Do not show "View in Studio" links for child verticals of verticals.

/request_cert AJAX endpoint

* Sample HTML and javascript to show how you might integrate the
  /request_certificate endpoint into a course.

Co-authored-by: Joe Blaylock <jrbl@jrbl.org>

* API endpoint for certificate generation, an authenticated  post with course
  id requests that grading be carried out and a cert generated for
  request.user in that course, using the usual grading and certificate
  machinery (ie, it does not imply whitelisting, though whitelists and
  blacklists will be respected)
  - Logs each request as it comes in
  - Calls xq.add_cert() and consequently, does grading synchronously on
    this app host and then queues request for certificate agent.
  - example usage:
    ```
    curl --data "student_id=9999&course_id=Stanford/2013/Some_Class" http://127.0.0.1:8000/request_certificate
    ```

* Studio advanced setting added, "certificates_show_before_end", which
  determines whether a course should permit certificates to be downloadable
  by students before the coures's end date has passed.
  - Modifications to dashboard view and templates to allow display of
    certificate download links before course has ended.
    (XXX: may declare failing students as failing before the course has ended.)
  - To test, turn the setting on in a course which hasn't ended yet, and
    force certificate generation for a student, then check their
    dashboard.

Adds very basic about page style to ul, ol and dl

About pages need basic support for lists since professors often want to display lists or 'definitions'

Expose "enabled" checkbox in Embargo admin

STUD-1558

Fixed link to docs.edx.org in readme

Parameter from_email to send_mail() should be string

Update drag and drop documentation

Fixes firefox image hidden overflow bug.

Release

LMS-2518

Add IFrame template documentation

Remove google analytics tracking from iframes used in Drupal course abou...

puts GA id in quotes

Disable draft and edit links during ajax calls

Add admin.py for instructor_task.

STUD-1485
STUD-1499

Certs: pass course name on queue

Create a skeleton of event-tracking developer docs

Integrate event-tracking in to the LMS

A first pass at providing details about how to emit events, what to emit etc.

Support incremental conversion of events from the old API to the new, in order to ensure the new system is working, enrollment events have been modified to make use of the new API.

Modifying the checkbox examples syntax so that it works in studio.edge now.

This is primarily so that we can manually fail zombie instructor
tasks that are clogging up the queue for a course.

Add documentation on public sandboxes

Fix bug that prevented account association during registration

Adding more about the --failed functionality

Issue certificates to all students who earn them, even if they are in an audit track