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.

common/static/common/js/discussion/mathjax_include.js

@@ -0,0 +1,36 @@
+var vendorScript;
+if (typeof MathJax === 'undefined') {
+    vendorScript = document.createElement('script');
+    vendorScript.onload = function() {
+        'use strict';
+        var MathJax = window.MathJax,
+            setMathJaxDisplayDivSettings;
+        MathJax.Hub.Config({
+            tex2jax: {
+                inlineMath: [
+                    ['\\(', '\\)'],
+                    ['[mathjaxinline]', '[/mathjaxinline]']
+                ],
+                displayMath: [
+                    ['\\[', '\\]'],
+                    ['[mathjax]', '[/mathjax]']
+                ]
+            }
+        });
+        MathJax.Hub.signal.Interest(function(message) {
+            if (message[0] === 'End Math') {
+                setMathJaxDisplayDivSettings();
+            }
+        });
+        setMathJaxDisplayDivSettings = function() {
+            $('.MathJax_Display').each(function() {
+                this.setAttribute('tabindex', '0');
+                this.setAttribute('aria-live', 'off');
+                this.removeAttribute('role');
+                this.removeAttribute('aria-readonly');
+            });
+        };
+    };
+    vendorScript.src = 'https://cdn.mathjax.org/mathjax/2.6-latest/MathJax.js?config=TeX-MML-AM_SVG';
+    document.body.appendChild(vendorScript);
+}

common/static/common/js/spec/discussion/view/discussion_thread_profile_view_spec.js

@@ -18,12 +18,6 @@
                 created_at: '2014-09-09T20:11:08Z'
             };
             this.imageTag = '<img src="https://www.google.com.pk/images/srpr/logo11w.png">';
-            window.MathJax = {
-                Hub: {
-                    Queue: function() {
-                    }
-                }
-            };
         });
         makeView = function(thread) {
             var view;