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/LoadingIndicator.js

@@ -0,0 +1,27 @@
+import Component from 'flarum/Component';
+
+/**
+ * The `LoadingIndicator` component displays a loading spinner with spin.js. It
+ * may have the following special props:
+ *
+ * - `size` The spin.js size preset to use. Defaults to 'small'.
+ *
+ * All other props will be assigned as attributes on the element.
+ */
+export default class LoadingIndicator extends Component {
+  view() {
+    const attrs = Object.assign({}, this.props);
+
+    attrs.className = 'loading-indicator ' + (attrs.className || '');
+    delete attrs.size;
+
+    return <div {...attrs}>{m.trust('&nbsp;')}</div>;
+  }
+
+  config() {
+    const size = this.props.size || 'small';
+
+    $.fn.spin.presets[size].zIndex = 'auto';
+    this.$().spin(size);
+  }
+}