ctrlKey event for selecting/deselecting files in folder tree (#1588)
ctrlKey event for selecting/deselecting files in folder tree (#1588)

* ctrlKey event for selecting/deselecting files in folder tree

* Needed to remove datasets that a deselected by ctrl+click

refs #1581

ngageoint/hootenanny-ui,ngageoint/hootenanny-ui,ngageoint/hootenanny-ui