refactor(nav): add initial support for url in general, add integration w/ ng-router

packages/angular/src/util/util.ts

@@ -15,3 +15,20 @@ export function ensureElementInBody(elementName: string) {
   }
   return element;
 }
+
+export function removeAllNodeChildren(element: HTMLElement) {
+  while (element.firstChild) {
+    element.removeChild(element.firstChild);
+  }
+}
+
+export function isString(something: any) {
+  return typeof something === 'string' ? true : false;
+}
+
+/**
+ * Flattens single-level nested arrays.
+ */
+export function flatten<T>(arr: T[][]): T[] {
+  return Array.prototype.concat.apply([], arr);
+}