Fix movement commands to parent node.

* python-django.el (python-django-ui-parent-widget-move)
(python-django-ui-parent-widget-forward)
(python-django-ui-parent-widget-backward): Remove.
(python-django-ui-move-up-tree): New command.
(python-django-ui-end-of-widgets)
(python-django-ui-beginning-of-widgets): Doc fix.