Remove google analytics tracking from iframes used in Drupal course about pages

This fixes two issues:
 - if the course pointed to doesn't exist, GA was added to the iframe twice
 - more importantly, we don't want to count these as separate views anyway--
   we just care about the about page itself.
 - I also added a note about where we would put our segment.io widget if we want it
   later

LMS-2581
Add admin.py for instructor_task.

This is primarily so that we can manually fail zombie instructor
tasks that are clogging up the queue for a course.
fixes firefox image hidden overflow bug.
puts GA id in quotes
Disable draft and edit links during ajax calls
STUD-1485
STUD-1499
Merge pull request #3274 from edx/ormsbee/instructor_task_admin_for_daves_vacation_enjoyment

Add admin.py for instructor_task.
Merge pull request #3560 from edx/adam/disable-links-ajax-2

Disable draft and edit links during ajax calls
Merge pull request #3564 from edx/adam-fix-GA-quotes

puts GA id in quotes
Merge pull request #3551 from edx/victor/remove-iframe-ga

Remove google analytics tracking from iframes used in Drupal course abou...
Update IFrame documentation
Merge pull request #3527 from edx/sylvia/docs/DOC-295

Add IFrame template documentation
Parameter from_email to send_mail() should be string and not string in list.

LMS-2518
Fixed link to docs.edx.org in readme
Merge pull request #3574 from edx/release

Release
Merge pull request #3562 from caesar2164/giulio/zoom-image-firefox-bugfix

Fixes firefox image hidden overflow bug.
Update drag and drop documentation
Merge pull request #3559 from edx/sylvia/docs/DOC-99

Update drag and drop documentation
Merge pull request #3417 from edx/usman/lms2518-refund-emails

Parameter from_email to send_mail() should be string
Merge pull request #3575 from edx/markhoeber/documentation/fix-link-in-readme

Fixed link to docs.edx.org in readme
Expose "enabled" checkbox in Embargo admin