Have DiscussionXBlock take care of loading JS and CSS files it depends on.

* 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.

lms/static/sass/_build-base-v1-rtl.scss

@@ -0,0 +1,9 @@
+// libs and resets *do not edit*
+@import 'bourbon/bourbon'; // lib - bourbon
+@import 'vendor/bi-app/bi-app-rtl'; // set the layout for right to left languages
+@import 'base/variables-rtl';
+
+// base - utilities
+@import 'base/reset';
+@import 'base/variables';
+@import 'base/mixins';

lms/static/sass/_build-base-v1.scss

@@ -0,0 +1,8 @@
+// libs and resets *do not edit*
+@import 'bourbon/bourbon'; // lib - bourbon
+@import 'vendor/bi-app/bi-app-ltr'; // set the layout for left to right languages
+
+// base - utilities
+@import 'base/reset';
+@import 'base/variables';
+@import 'base/mixins';

lms/static/sass/_build-course.scss

@@ -59,10 +59,6 @@
 // course - ccx_coach
 @import "course/ccx_coach/dashboard";
 
-// discussion
-@import "course/discussion/form-wmd-toolbar";
-@import "course/discussion/form";
-
 // search
 @import 'search/_search';
 

lms/static/sass/_build-lms-v1.scss

@@ -61,22 +61,6 @@
 @import 'course/auto-cert';
 @import 'views/api-access';
 
-// app - discussion
-@import "discussion/utilities/variables-v1";
-@import "discussion/mixins";
-@import 'discussion/discussion'; // Process old file after definitions but before everything else, partial is deprecated.
-@import 'discussion/discussion-v1'; // Non-Pattern Library styling
-@import "discussion/elements/actions";
-@import "discussion/elements/editor";
-@import "discussion/elements/labels";
-@import "discussion/elements/navigation";
-@import "discussion/views/home";
-@import "discussion/views/thread";
-@import "discussion/views/create-edit-post";
-@import "discussion/views/response";
-@import 'discussion/utilities/developer';
-@import 'discussion/utilities/shame';
-
 // search
 @import 'search/search';
 

lms/static/sass/discussion/_build-discussion.scss

@@ -0,0 +1,27 @@
+// ------------------------------
+// Discussions: Shared Build Compile
+
+// About: Sass compile for discussion elements that are shared between LTR and RTL UI. Configuration and vendor specific imports happen before this shared set of imports is compiled in the inline-discussion-*.scss files.
+
+// Set the relative path to the static root
+$static-path: '../..';
+
+// Styles for discussions
+@import "utilities/variables-v1";
+@import "mixins";
+@import 'discussion'; // Process old file after definitions but before everything else, partial is deprecated.
+@import 'discussion-v1'; // Non-Pattern Library styling
+@import "elements/actions";
+@import "elements/editor";
+@import "elements/labels";
+@import "elements/navigation";
+@import "views/home";
+@import "views/thread";
+@import "views/create-edit-post";
+@import "views/response";
+@import 'utilities/developer';
+@import 'utilities/shame';
+
+// Styles for WYSIWYG Markdown editor
+@import "../course/discussion/form-wmd-toolbar";
+@import "../course/discussion/form";

lms/static/sass/discussion/inline-discussion-rtl.scss

@@ -0,0 +1,11 @@
+// Discussions - CSS application architecture
+// Version 1 styling (pre-Pattern Library)
+// ====================
+
+@import '../build-base-v1-rtl';
+
+// base - elements
+@import '../elements/typography';
+
+// app - discussion
+@import 'build-discussion';

lms/static/sass/discussion/inline-discussion.scss

@@ -0,0 +1,11 @@
+// Discussions - CSS application architecture
+// Version 1 styling (pre-Pattern Library)
+// ====================
+
+@import '../build-base-v1';
+
+// base - elements
+@import '../elements/typography';
+
+// app - discussion
+@import 'build-discussion';

lms/static/sass/lms-main-v1-rtl.scss

@@ -2,17 +2,5 @@
 // Version 1 styling (pre-Pattern Library)
 // ====================
 
-// libs and resets *do not edit*
-@import 'bourbon/bourbon'; // lib - bourbon
-@import 'vendor/bi-app/bi-app-rtl'; // set the layout for right to left languages
-@import 'base/variables-rtl';
-
-// BASE  *default edX offerings*
-// ====================
-
-// base - utilities
-@import 'base/reset';
-@import 'base/variables';
-@import 'base/mixins';
-
+@import 'build-base-v1-rtl';
 @import 'build-lms-v1'; // shared app style assets/rendering

lms/static/sass/lms-main-v1.scss

@@ -2,16 +2,5 @@
 // Version 1 styling (pre-Pattern Library)
 // ====================
 
-// libs and resets *do not edit*
-@import 'bourbon/bourbon'; // lib - bourbon
-@import 'vendor/bi-app/bi-app-ltr'; // set the layout for left to right languages
-
-// BASE  *default edX offerings*
-// ====================
-
-// base - utilities
-@import 'base/reset';
-@import 'base/variables';
-@import 'base/mixins';
-
+@import 'build-base-v1';
 @import 'build-lms-v1'; // shared app style assets/rendering