TEIIDDES-1724: Stops active editor selection if object is a descendent

* When opening an editor, the default behaviour is to find the file that
  is the input of the editor. This file is then selected in the model
  explorer if 'link with editor' is enabled.

* Behaviour changed to check whether the file being selected in the model
  explorer is the container of the currently selected object. If it is
  then do not change the selection.