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/ModalManager.js

@@ -0,0 +1,82 @@
+import Component from 'flarum/Component';
+import Modal from 'flarum/components/Modal';
+
+/**
+ * The `ModalManager` component manages a modal dialog. Only one modal dialog
+ * can be shown at once; loading a new component into the ModalManager will
+ * overwrite the previous one.
+ */
+export default class ModalManager extends Component {
+  view() {
+    return (
+      <div className="modal">
+        {this.component && this.component.render()}
+      </div>
+    );
+  }
+
+  config(isInitialized) {
+    if (isInitialized) return;
+
+    this.$()
+      .on('hidden.bs.modal', this.clear.bind(this))
+      .on('shown.bs.modal', this.onready.bind(this));
+  }
+
+  /**
+   * Show a modal dialog.
+   *
+   * @param {Modal} component
+   * @public
+   */
+  show(component) {
+    if (!(component instanceof Modal)) {
+      throw new Error('The ModalManager component can only show Modal components');
+    }
+
+    clearTimeout(this.hideTimeout);
+
+    this.component = component;
+
+    m.redraw(true);
+
+    this.$().modal('show');
+    this.onready();
+  }
+
+  /**
+   * Close the modal dialog.
+   *
+   * @public
+   */
+  close() {
+    // Don't hide the modal immediately, because if the consumer happens to call
+    // the `show` method straight after to show another modal dialog, it will
+    // cause Bootstrap's modal JS to misbehave. Instead we will wait for a tiny
+    // bit to give the `show` method the opportunity to prevent this from going
+    // ahead.
+    this.hideTimeout = setTimeout(() => this.$().modal('hide'));
+  }
+
+  /**
+   * Clear content from the modal area.
+   *
+   * @protected
+   */
+  clear() {
+    this.component = null;
+
+    m.redraw();
+  }
+
+  /**
+   * When the modal dialog is ready to be used, tell it!
+   *
+   * @protected
+   */
+  onready() {
+    if (this.component && this.component.onready) {
+      this.component.onready(this.$());
+    }
+  }
+}