Lookup itemViewClass and emptyView of collectionView if given as string

Fixes #3116

If itemViewClass and emptyView of collectionView is given as string, look
it up on the current view first, then fallback to the container.
added ember-testing integration test for issue #2997
Merge pull request #3026 from toranb/master

added ember-testing integration test for issue #2997
Merge pull request #3175 from hyderali/emptyview-issuefix

Lookup itemViewClass and emptyView of collectionView if given as string
simplify emptyView and itemViewClass lookups.
Continue to make view creation container aware

- Ember.View#createChildView will attempt to construct a view given a string viewName
- Simplify Ember.CollectionView itemViewClass + emptyView lookups to piggy back on createChildView container aware view creation
Initial Query Params Implementation