Fixed inline widgets sometimes not getting updated

gui/pipeline_view.py:
  - function_changed:
    self.module does not get updated correctly so get module from controller instead
  - update_function_values: *new
  - functions_have_been_deleted: *new
  - hoverEnterEvent:
    Set widget on scene instead so that it never gets orphaned
  - setupScene:
    Call update_function_values

Ticket: 903