Make django-debug-toolbar >= 1.0 work properly with syncdb and admin.

The autodiscovery used by admin will interact badly with Django
Debug Toolbar's own auto-setup. So we have to be more explicit about
everything and add some settings manually. See:

http://django-debug-toolbar.readthedocs.org/en/1.0/installation.html#explicit-setup
Merge pull request #171 from edx/ormsbee/django_toolbar_settings_fix

Make django-debug-toolbar >= 1.0 work properly with syncdb and admin.