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/LinkButton.js

@@ -0,0 +1,32 @@
+import Button from 'flarum/components/Button';
+
+/**
+ * The `LinkButton` component defines a `Button` which links to a route.
+ *
+ * ### Props
+ *
+ * All of the props accepted by `Button`, plus:
+ *
+ * - `active` Whether or not the page that this button links to is currently
+ *   active.
+ * - `href` The URL to link to. If the current URL `m.route()` matches this,
+ *   the `active` prop will automatically be set to true.
+ */
+export default class LinkButton extends Button {
+  static initProps(props) {
+    props.active = this.isActive(props);
+    props.config = props.config || m.route;
+  }
+
+  /**
+   * Determine whether a component with the given props is 'active'.
+   *
+   * @param {Object} props
+   * @return {Boolean}
+   */
+  static isActive(props) {
+    return typeof props.active !== 'undefined'
+      ? props.active
+      : m.route() === props.href;
+  }
+}