Initial stab at breadcrumbs

There's currently a lot of copy-pasting of breadcrumbs, this can be revisited once we have a better understanding of how we're going to handle navigation.

I've also tried to make template context variables more logical and consistent throughout.
Update AUTHORS.rst
add missing test for utils.model_app_label
Rename app-index view to app_index
Merge branch 'breadcrumbs' of git://github.com/AndrewIngram/django-admin2 into AndrewIngram-breadcrumbs
Implementing a class-based permission handling.
Moving permission logic of views into its own mixin. Also allow to check permission on other views via the PermissionMixin.
Adding the ability to check for permissions in templates.
Setting up autodoc for the docs.

For this to work you need to install sphinx in your virtualenv. It's added to
the requirements.txt so just run: pip install -r requirements.txt
Adding reference documentation for permission handling.
Adding documentation about how to use permissions in the template.
Allow ModelAdmin2 instances to have names.
Adding ability to check for permissions of any registered model admin in the templates.
Adding possibility to swap model admin that is checked for permissions in the template.
Adding possibility to traverse permissions by admin name.
Adding |for_view filter to bind permissions for a view name.
Adding more information to the docstring of the template permission handler.
Re-writing the docs about the permission handling.
Adding a IsSuperuserPermission class.
Removing old permission handling.