This change adds a few new things to RB.CollectionView:

- The view will properly respond when the collection is reset.

- The view will reorder DOM elements for sorted collections.

- The itemViewType can be passed in as an option at construction time, rather

  than requiring CollectionView to be extended.

- A new itemViewOptions member allows options to be plumbed through to the

  individual item views.

Used these features in another change (in Power Pack).