refactor(router): use ApplicationRef to provide the first bootstrapped component as ROUTER_PRIMARY_COMPONENT automatically.

This removes the routerBindings function as it is no longer necessary. ROUTER_BINDINGS will automatically pick the first bootstrapped component to satisfy ROUTER_PRIMARY_COMPONENT.

BREAKING CHANGE:

Before: bootstrap(MyComponent, [routerBindings(myComponent)]);
After: bootstrap(MyComponent, [ROUTER_BINDINGS]);

Closes #4643

modules/angular2/test/public_api_spec.ts

@@ -90,6 +90,7 @@ var NG_API = [
   'ApplicationRef:js',
   'ApplicationRef.injector:js',
   'ApplicationRef.zone:js',
+  'ApplicationRef.componentTypes:js',
   /*
   Abstract methods
   'ApplicationRef.bootstrap()',