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/components/Select.js

@@ -0,0 +1,25 @@
+import Component from 'flarum/Component';
+import icon from 'flarum/helpers/icon';
+
+/**
+ * The `Select` component displays a <select> input, surrounded with some extra
+ * elements for styling. It accepts the following props:
+ *
+ * - `options` A map of option values to labels.
+ * - `onchange` A callback to run when the selected value is changed.
+ * - `value` The value of the selected option.
+ */
+export default class Select extends Component {
+  view() {
+    const {options, onchange, value} = this.props;
+
+    return (
+      <span className="select">
+        <select className="form-control" onchange={m.withAttr('value', onchange.bind(this))} value={value}>
+          {Object.keys(options).map(key => <option value={key}>{options[key]}</option>)}
+        </select>
+        {icon('sort', {className: 'caret'})}
+      </span>
+    );
+  }
+}