768498 more access control

DO NOT MERGE without first getting these commits squashed and merging changes to kuma-lib

I think this is at a point for more eyes on it. This pulls in updates to django-teamwork, and adds on-site UI for managing team roles and access policies on wiki documents. It also adds [django-grappelli](http://grappelliproject.com/) for a slicker admin UI.

To spot check the policies:
* login as admin
* check the "This Page" menu
* you should see an item "Add access policy", which leads to the admin UI to create a new Policy
* after creating a policy, the "This Page" menu item should change to "Manage access policy", which leads to editing the policy you just created
* if you create an additional policy within admin, the menu item changes to "Manage access policies", which leads to a list of the multiple access policies for that wiki page

To spot check the team stuff:
* login as admin
* go to the admin UI, add a team and some roles
* visit a user profile on the site
* there should be a "Manage Roles" button
* when you click that button, you should get an ugly page that lets you grant & revoke roles for that user