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/DeleteAccountModal.js

@@ -0,0 +1,67 @@
+import Modal from 'flarum/components/Modal';
+
+/**
+ * The `DeleteAccountModal` component shows a modal dialog which allows the user
+ * to delete their account.
+ *
+ * @todo require typing password instead of DELETE
+ */
+export default class DeleteAccountModal extends Modal {
+  constructor(props) {
+    super(props);
+
+    /**
+     * The value of the confirmation input.
+     *
+     * @type {Function}
+     */
+    this.confirmation = m.prop();
+  }
+
+  className() {
+    return 'modal-sm delete-account-modal';
+  }
+
+  title() {
+    return 'Delete Account';
+  }
+
+  content() {
+    return (
+      <div className="modal-body">
+        <div className="form-centered">
+          <div className="help-text">
+            <p>Hold up! If you delete your account, there&#39;s no going back. Keep in mind:</p>
+            <ul>
+              <li>Your username will be released, so someone else will be able to sign up with your name.</li>
+              <li>All of your posts will remain, but no longer associated with your account.</li>
+            </ul>
+          </div>
+          <div className="form-group">
+            <input className="form-control"
+              name="confirm"
+              placeholder="Type &quot;DELETE&quot; to proceed"
+              oninput={m.withAttr('value', this.confirmation)}/>
+          </div>
+          <div className="form-group">
+            <button type="submit"
+              className="btn btn-primary btn-block"
+              disabled={this.loading || this.confirmation() !== 'DELETE'}>
+              Delete Account
+            </button>
+          </div>
+        </div>
+      </div>
+    );
+  }
+
+  onsubmit(e) {
+    e.preventDefault();
+
+    if (this.confirmation() !== 'DELETE') return;
+
+    this.loading = true;
+
+    app.session.user.delete().then(() => app.session.logout());
+  }
+}