Update the VideoModule to publish a completion event when the player
reaches 95% complete, and submit a BlockCompletion when that event
occurs.

OC-3091
MCKIN-5897

In the absence of an EDX_PLATFORM_VERSION OS env variable, we used to
calculate the current version by looking at the current git revision of
the edx-platform repo. This was an expensive calculation (~7% of startup
costs). It also turns out that at some point we stopped setting that env
variable anywhere, so it always fell back to recalculating it.

With this commit, we'll start reading the code version from the env JSON
files, and fall back to "unknown" rather than doing the dealer.git call.

Add accessibility accomodation request page to studio and link to said page in footer, both behind a Waffle switch. Add tests for the new page.

The LMS and edx-enterprise currently communicate via REST APIs, even
though they are all running within the same service.

Currently API URLs are constructed using LMS_ROOT_URL, but that is
problematic on some systems where the external LMS_ROOT_URL is not
accessible from the private network, or routing internal requests via
the external URL is not desireable.

This patch introduces a new setting variable LMS_INTERNAL_ROOT_URL which
defaults to the value of LMS_ROOT_URL for backwards compatibility.

The LMS and edx-enterprise will use LMS_INTERNAL_ROOT_URL to construct
API URLs instead of LMS_ROOT_URL.

EDUCATOR-1335 - This Adds a dedicated app which is responsible for communication with edx-video-pipeline service. It also adds the backend for saving 3rd party transcription service credentials on edx-video-pipline and cache it in edx-val.

This also creates a new app common_initialization in order to provide a
place to run initialization code common to both the LMS and CMS.

  all dirs must now go into COMPREHENSIVE_THEME_DIRS.
Move comprehensive theming setup section out of startup.py and into
  settings files using new 'derived' functionality.
Add 'derive_settings' at the end of all top-level Django settings files.
Move validation of comprehensive theming settings into new apps.py
  theming file.
Split theming code into code safe to run before settings are initialized
  -and- after settings are initialized.

This fixes a bug introduced in 3be0fa81

EDUCATOR-1448

Modifies paver webpack task to use production configuration in all
non-devstack environments, and a development config in devstack.

The module is still used by (at least) edx-enterprise.