Massive JavaScript cleanup

- Use JSX for templates
- Docblock/comment everything
- Mostly passes ESLint (still some work to do)
- Lots of renaming, refactoring, etc.

CSS hasn't been updated yet.

js/lib/extend.js

@@ -0,0 +1,75 @@
+/**
+ * Extend an object's method by running its output through a mutating callback
+ * every time it is called.
+ *
+ * The callback accepts the method's return value and should perform any
+ * mutations directly on this value. For this reason, this function will not be
+ * effective on methods which return scalar values (numbers, strings, booleans).
+ *
+ * Care should be taken to extend the correct object – in most cases, a class'
+ * prototype will be the desired target of extension, not the class itself.
+ *
+ * @example
+ * extend(Discussion.prototype, 'badges', function(badges) {
+ *   // do something with `badges`
+ * });
+ *
+ * @param {Object} object The object that owns the method
+ * @param {String} method The name of the method to extend
+ * @param {function} callback A callback which mutates the method's output
+ */
+export function extend(object, method, callback) {
+  const original = object[method];
+
+  object[method] = function(...args) {
+    const value = original.apply(this, args);
+
+    callback.apply(this, [value].concat(args));
+
+    return value;
+  };
+}
+
+/**
+ * Override an object's method by replacing it with a new function, so that the
+ * new function will be run every time the object's method is called.
+ *
+ * The replacement function accepts the original method as its first argument,
+ * which is like a call to 'super'. Any arguments passed to the original method
+ * are also passed to the replacement.
+ *
+ * Care should be taken to extend the correct object – in most cases, a class'
+ * prototype will be the desired target of extension, not the class itself.
+ *
+ * @example
+ * override(Discussion.prototype, 'badges', function(original) {
+ *   const badges = original();
+ *   // do something with badges
+ *   return badges;
+ * });
+ *
+ * @param {Object} object The object that owns the method
+ * @param {String} method The name of the method to override
+ * @param {function} newMethod The method to replace it with
+ */
+export function override(object, method, newMethod) {
+  const original = object[method];
+
+  object[method] = function(...args) {
+    return newMethod.apply(this, [original.bind(this)].concat(args));
+  };
+}
+
+/**
+ * Register a notification type.
+ *
+ * @param {String} name The name of the notification type (equivalent to the
+ *     serialized `contentType`)
+ * @param {Object} Component The constructor of the component that this
+ *     notification type should be rendered with
+ * @param {String|Array} label vDOM to render a label in the notification
+ *     preferences grid for this notification type
+ */
+export function notificationType(name, Component, label) {
+  // TODO
+}