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/forum/src/components/SearchSource.js

@@ -0,0 +1,32 @@
+/**
+ * The `SearchSource` interface defines a section of search results in the
+ * search dropdown.
+ *
+ * Search sources should be registered with the `Search` component instance
+ * (app.search) by extending the `sourceItems` method. When the user types a
+ * query, each search source will be prompted to load search results via the
+ * `search` method. When the dropdown is redrawn, it will be constructed by
+ * putting together the output from the `view` method of each source.
+ *
+ * @interface
+ */
+export default class SearchSource {
+  /**
+   * Make a request to get results for the given query.
+   *
+   * @param {String} query
+   * @return {Promise}
+   */
+  search() {
+  }
+
+  /**
+   * Get an array of virtual <li>s that list the search results for the given
+   * query.
+   *
+   * @param {String} query
+   * @return {Object}
+   */
+  view() {
+  }
+}