Selection issues with link with editor

* The DeleteWorker assigns the selected objects to the delete command
  during its execution phase. However, during the pre-run phase, the
  model editors associated with the selected objects are opened. If the
  'link with editor' option is selected then the focus on the editor
  causes the selection to change PRIOR to the execution phase.

* DeleteEObjectAction
 * Assigns the selected objects to the DeleteWorker at the start of the
   pre-run phase

* DeleteWorker
 * Caches the selected objects when the set method is called

* Convert multiple uses of arrays into lists