``RoutePartitionerTokeniserTest`` can now be run headless-ly

* Renamed ``Util`` to ``EditorUI`` because ``defaultLineSeparator`` requires
  loading some UI class, and that is a problem because our CI server can only
  build headless-ly. Hen

* Created ``Editor`` and ``Util.getEditorDocument`` on it.

* ``RoutePartitionTokeniser`` tries to be robust against any kind of line separator.

The failure was introduced in SHA: 6b796dbde3547b0bf445aa19a30b37998c74d16d