Allow to control which of the optional fields from the registration page
are being displayed to the user. Added the configuration variable
`REGISTRATION_OPTIONAL_FIELDS` to control which ones. The default value
shows all the fields as currently; to not display some of the fields,
set the configuration variable with only the fields you want to display:

```
REGISTRATION_OPTIONAL_FIELDS = [
    'level_of_education',
    'gender',
    'year_of_birth',
    'mailing_address',
    'goals'
]
```

Video player: fix start-end time bugs.

add error handling for update_score for OEE when no child_history

Course creation form cleanup

updated course creation UI: placeholder text for Org is now more generic, run is now using current format, and tips are now below fields to allow more room for tip text
Addresses bugs STUD-885 and STUD-916

Studio: Fix - Forgot Password Modal

STUD-689

Make export URL restful.

Remove label from forum posts by global staff

Fix AssertionErrors that were raised when creation of an XModule failed

Improve accessibility of forum follow buttons

Will/acceptance test fixes

Course id clash command

Added wait for JS on upload page
Fixed an issue where css_click wasn't waiting for JS to load

The motivation for this change is performance. The forums UI code gets
the list of users for each role and renders the staff label based on
those lists. The list for the staff role is expensive to compute because
there is no index on the is_staff attribute, and we cannot create one
because the User model is built into django.

Users with is_staff=True are still assigned the Moderator role upon
enrolling in a course, so this change will have no practical effect
except that a user who is granted staff privileges after enrolling in a
course will have to be made a Moderator in order for their posts to be
labeled.

Additionally, the UI did not use the list of users with the Student
role, so that list has been removed as well.

Implement background email tasks on student dash

The ErrorDescriptor wasn't getting the appropriate xmodule_runtime set,
and thus immediately raising an AssertionError when we tried to retrieve
and _xmodule from it.

[LMS-1388[

LMS-1244

Anton/word cloud total count in studio bug

Hotfix 2013 10 31

Proper abstraction of Module store base class implemented

Add skip link to django template pages.

Fixing accessibility bug where users could not tab through on wiki

Add datadog stats for duplicate subtask and subtask update errors.

Bug: LMS-1387

They now include screen reader-friendly text, have the ARIA checkbox
role, activate on keypress (for space or enter), and occur in the DOM
after the header information (title, etc.)

Clean up pep8/pylint

Bug fix: video end time proper seek beyond.

Fix bug when the user clicks on the video time-line either
before or after the specified end time, it jumps
to the very beginning of the video.

BLD-392

Video Player: Disallow users to enter video url's in http.

Package the instructor dash javascript separately