docs(aio): rename cb- files and a few others

aio/content/examples/dynamic-form/src/app/question-dropdown.ts

@@ -0,0 +1,12 @@
+// #docregion
+import { QuestionBase } from './question-base';
+
+export class DropdownQuestion extends QuestionBase<string> {
+  controlType = 'dropdown';
+  options: {key: string, value: string}[] = [];
+
+  constructor(options: {} = {}) {
+    super(options);
+    this.options = options['options'] || [];
+  }
+}