feat(router): provide RouteConfig object for AuxRoute

Right now, you must do:

```
@RouteConfig([
  new AuxRoute({ path: '/foo', component: FooCmp })
])
```

To use auxiliary routes. We should provide a more ES5-friendly version like:

```
@RouteConfig([
  { auxPath: '/foo', component: FooCmp }
])
```

Or:

```
@RouteConfig([
  { path: '/foo', auxComponent: FooCmp }
])
```

I'm open to suggestions.
