feat(router): add interfaces for route definitions in RouteConfig

Closes #2261

modules/angular2/test/router/route_config_spec.dart

@@ -0,0 +1,9 @@
+library angular2.test.router.route_config_spec;
+
+/**
+ * This is intentionally left blank. `route_config_spec.ts` contains tests specific
+ * to using untyped objects for users writing idiomatic ES5 or TS.
+ * The rest of the router tests have typed annotations, so there's no need to add
+ * additional tests here for Dart.
+ */
+main () {}