Workbench collection operations should use the replace_files API (See: https://doc.arvados.org/v2.5/api/methods/collections.html#replace_files).
* Rename files or directories
* Remove files or directories
* Create a new collection from selected files
* Copy selected files to an existing collection (was implemented previously, is presently commented out)
New operations -- these should be basically the same as the copy operations except that files are removed from their original collection locations.
* Move files or directories to a new collection
* Move files or directories to an existing collection
* Copy/move to existing collection should work when the source and destination collection are the same (i.e. within the same collection)
* When opening a dialog to move or copy files to a collection, the dialog should start with the current collection selected.