Clean up some instructor dash code
Adds Staff and Instructor factories
Do JS setup immediately when possible
Acceptance tests use asset pipeline
registration-optional: Allow to hide some optional registration fields

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'
]
```
Removed duplicate code
Fix instructor api tests
Merge pull request #1589 from edx/flowerhack/fix/remove-duplicate-course-helper-code

Removed duplicate code
If the YouTube API JS fails to load, the rest of the JS should still run

Fixes BLD-472
Merge pull request #1579 from edx/sarina/enhance-user-factories

Sarina/enhance user factories
Merge pull request #1590 from edx/db/youtube-fallback

If the YouTube API JS fails to load, the rest of the JS should still run
setting THEME_NAME to None when it's set to an empty string
Add retries when encountering DatabaseError when updating InstructorTask.
Merge pull request #1585 from edx/brian/retry-email-after-dbtimeout

Add retries when encountering DatabaseError when updating InstructorTask.
Merge pull request #1591 from edx/jarv/theme-name

setting THEME_NAME to None when it's set to an empty string
Merge pull request #1581 from antoviaque/registration-optional

registration-optional: Allow to hide some optional registration fields #os
Merge pull request #1571 from edx/db/js-main-setup

Do JS setup immediately when possible
Added tests to video player controls to check new WAI-ARIA functionality. Added global custom Jasmine matcher to helper.coffee

[BLD-386]
Merge pull request #1574 from edx/jmclaus/feature_tests_video_player_controls_a11y

 a11y tests for video player controls [BLD-386]
LMS: add CSRF token to register form