TEIIDDES-1929: Stricter policy on allowing deletions with open editors

* When deleting, resources are unloaded and closed. This can lead to odd
  updates to open editors

* Delete is the only refactoring to allow the operation whilst editors are
  open. This is fine if an editor for the resource being deleted is open
  since the editor gets closed anyway. However, it can be a problem for
  related resource editors, especially if the delete is cancelled. The
  resources are not reloaded and the editor never refreshed

* Check for open editors of related resources and just get the user to
  close it first before proceeding.

plugins/org.teiid.designer.ui/src/org/teiid/designer/ui/refactor/delete/DeleteResourcesRefactoring.java

@@ -150,6 +150,16 @@ protected void checkResource(IResource resource, IProgressMonitor progressMonito
         if (status.getSeverity() > IStatus.WARNING) return;
 
         RefactorResourcesUtils.checkSavedResource(resource, status);
+      if (status.getSeverity() > IStatus.WARNING) return;
+
+      if (! getResources().contains(resource)) {
+          /*
+           * Its okay to delete a resource if an editor for it is open but can cause
+           * problems for related resources, especially if the user previews then
+           * cancels the delete operation.
+           */
+          RefactorResourcesUtils.checkOpenEditors(resource, status);
+      }
     }
 
     @Override