Enhancements to management command handling.

* python-django.el:
(python-django-mode-map): Use new commands.
(python-django-mgmt-buffer-list): Rename from
python-django-mgmt-opened-buffers-for.
(python-django-mgmt-kill-all): Ask confirmation only when called
interactively.
(python-django-mgmt-kill): New command.
(python-django-mgmt--buffer-index): Rename from
python-django-ui-cycle-mgmt-opened-buffers-index.
(python-django-ui-cycle-mgmt-opened-buffers-forward): Remove
command.
(python-django-mgmt-cycle-buffers-forward): New command.
(python-django-ui-cycle-mgmt-opened-buffers-backward): Remove
command.
(python-django-mgmt-cycle-buffers-backward): New command.