RemoveEntry - Remove entry from reference (Del)

The remove entry action will be activated for controls referring to not owning collections, only. When the data source is not a reference or relationship or when the collection does own its instances, the action is inactive and cannot be called.

When no instance is currently selected in the data source, the action will be disabled.

When calling the action, it will remove the currently selected instance without warning or message. In order to receive a warning message before deleting an instance the GUIFramework .Query.Delete option should be set (see "Option browser")