TNL-5084

* Add openedx.core.lib.xblock_builtin.get_css_dependencies and get_js_dependencies,
  which respect PIPELINE_ENABLED setting when determining dependencies.
* Move new discussion-related Sass files into discussion subdirectory.
* Use "load_unicode" instead of "render_template" to load JS to add to fragment for DiscussionXBlock.
* Remove unused "course" parameter from context for DiscussionXBlock.student_view.
* Add RTL stylesheet for DiscussionXBlock, and enable the block to load correct stylesheet.
* Load MathJax only once, and include code for configuring MathJax in discussion bundle.
* Make sure username renders correctly in DiscussionXBlock response header.
* Move WYSIWYIG Markdown editor styles to _build-discussion.scss.
* Remove unnecessary import of discussion/utilities/v1-compatibility from _build-discussion.scss.
* Keep courseware-chromeless.html in sync with courseware.html.
* Load CSS for discussions on Teams tab.  This makes it possible to remove CSS for discussions from Sass files for "Course" tab.
* Load js/src/tooltip_manager.js, jquery.autocomplete.js and jquery.autocomplete.css on "Course" tab.

* Add openedx.core.lib.xblock_builtin.get_css_dependencies and get_js_dependencies,
  which respect PIPELINE_ENABLED setting when determining dependencies.
* Move new discussion-related Sass files into discussion subdirectory.
* Use "load_unicode" instead of "render_template" to load JS to add to fragment for DiscussionXBlock.
* Remove unused "course" parameter from context for DiscussionXBlock.student_view.
* Add RTL stylesheet for DiscussionXBlock, and enable the block to load correct stylesheet.
* Load MathJax only once, and include code for configuring MathJax in discussion bundle.
* Make sure username renders correctly in DiscussionXBlock response header.
* Move WYSIWYIG Markdown editor styles to _build-discussion.scss.
* Remove unnecessary import of discussion/utilities/v1-compatibility from _build-discussion.scss.
* Keep courseware-chromeless.html in sync with courseware.html.
* Load CSS for discussions on Teams tab.  This makes it possible to remove CSS for discussions from Sass files for "Course" tab.
* Load js/src/tooltip_manager.js, jquery.autocomplete.js and jquery.autocomplete.css on "Course" tab.

Allows staff using "view as specific student" mode to bypass edx-proctoring
hiding special exams from students, to allow for more useful debugging.

Includes "shim" pattern library implementation of alerts, and a bokchoy
test for this functionality.

This was originally contributed upstream by Stanford, circa 2013.

We neither use nor support this feature in its current implementation,
and in fact, we may never have used this production. Until recently, we
had additional chat/Jabber code [1] (in the form of a Jabber djangoapp in
LMS); context there suggests this feature may have never been more than
a prototype. The original author is no longer on the team, so I can't directly
confirm this on our end.

Do you use this feature?

Stanford had already abandoned this Jabber-backed chat implementation,
in favor of an IRC backend, by the time I joined the team in early 2014.

[1] https://github.com/Stanford-Online/edx-platform/commit/dbe52a6b133ab6ff637dea5324f7322da2909070

Co-Authored-By: Jean-Michel Claus <jmc@edx.org>
Co-Authored-By: Brian Talbot <btalbot@edx.org>
Co-Authored-By: Tim Babych <tim@edx.org>
Co-Authored-By: Oleg Marshev <oleg@edx.org>
Co-Authored-By: Chris Rodriguez <crodriguez@edx.org>

Adds a new Email link to the instructor dashboard for frontend interface to send
email to course members. Adds a feature flag ENABLE_INSTRUCTOR_EMAIL to toggle this.
Creates a new djangoapp bulk_email that handles this action by getting the recipient
list and batching the emails to different celery tasks to do the actual sending.
Requires lynx package to convert HTML email to plaintext. Handles SMTP errors by
retrying or falling through to the next email. Adds the option to opt out of course
specific emails in the user dashboard with an Email Settings link for each course.
Uses severable configurable settings with defaults. DEFAULT_BULK_FROM_EMAIL
specifies the from address for email. EMAILS_PER_TASK specifies the number of emails
each celery task takes on. EMAIL_HOST, EMAIL_PORT, EMAIL_HOST_USER,
EMAIL_HOST_PASSWORD, and EMAIL_USE_TLS for the SMTP email backend settings.

Co-authored-by: Akshay Jagadeesh <akjags@gmail.com>

Embed a chat widget (much like the calculator widget) into the
courseware. To use, you must point it at an ejabberd box,
configured as `JABBER_DOMAIN` in the settings.

Just as is done with the main LMS application.scss file, rewrite the
course.scss file with Mako to conditionally import a theme's
variables overrides. Add the course.scss file to the list of ignored
Git files so that it doesn't keep getting committed over and over
again.

This also requires us to add a hardcoded line in the assets Rakefile
for the moment, so that the course.scss.mako file gets properly
preprocessed. Once the preprocessing is done by a Django management
command, we won't have to do this anymore.

This allows us to a) compile the coffeescript and sass from xmodules
using the new out-of-band method and b) reload xmodule static content
whenever it changes, which should make devs much happier.

The unused styles are referencing images that no longer exisit,
breaking collectstatic and therefore tests.

scss files that were still being partially used by the current
discussion forum.

This reverts commit 010bccc8.