parentCollectionID is optional and defaults to moving item to root
Returns true on success, false on attempt to move collection into its existing parent, itself or a descendent collection; throws exception on invalid parentCollectionID
Sends a columnTree notify() with previous parent ID, id of collection itself, and new parent ID (unless the previous or new are the root, in which case it's omitted) -- that may or may not make sense for the interface code and can be changed if needed