Fixed module urls creation in legacy instructor dashboard.

LMS-2327
Fix Firefox YouTube default Flash mode

BLD-895
Fixed course update css to match changed tags
Don't close modal on click outside new course update modal.
STUD-1404
Make course_id a required arg to split.create_course
and remove attempt to make it unique. Instead raise exception on dupe.
STUD-1359
Put language modal in alphabetical order LMS-2302
Course Image and Dates documentation changes

stud-1272
Add a missing comment documenting the changes done in PR 2841.
Generalize grade report to allow display of any report

We would like to be able to generate arbitrary reports and expose them to the instructor by simply uploading them to S3.  The existing grade download infrastructure pretty much supported that already, however, all of the internal and external structures were referring to the reports as exclusively grading related.

Fixes: AN-590
DO NOT MERGE: hardwired ux code for changing static pages to pages and allowing course nav manipulation
cleaning up the UI to match current story better
cleaning up the html and style for pages in Studio
Changed "Status Page" -> "Page".
Display list of "built-in tabs" on Pages page.

Added defensive code for tabs that do not have the 'name' field stored in the database.  This is short-term solution until the LMS and CMS code is refactored.
Changed CSS class from locked to fixed.
additional styling for fixed state on Studio Pages
add a new page action added to bottom of Studio Pages
restoring drag and drop on Studio Pages

Dev changes for viewing tabs and refactoring the tab code.