added setCollection function to CollectionView

Why: When using a CollectionView or CompostiveView, I had a need to change the collection used in the view. Simply setting myView.collection = myOtherCollection caused problems when the original collection had items added. Using this setCollection function I wrote solves this.

What: a new function in CollectionView called setCollection. This function will be inherited to CompositeView.

How: unbind to the collection a view has and bind to the new collection.