Make Router.map callbacks invoke after application boot.
[FEATURE ember-routing-named-substates]

Only add loading and error substates if the resolver being used is a
modules based resolver.

Also, return the Ember.Router from `Ember.Router.map` instead of the
`router.js` router.
Merge pull request #9994 from machty/router-map-named-substates

[FEATURE ember-routing-named-substates]