Add admin views unit tests

For keyvalue and hwdoc projects since these are for now the only two to
actually register in the admin interface
Fix bug in hwdoc's admin views

Unit tests unveiled a bug where if a authenticated but not authorized
user tried to access some hwdoc admin URLs a 500 error would be return
because no ModelAdmin instance would be created. Make sure a ModelAdmin
instance is always returned regardless of the rights of the user
Drop support for django 1.2 and earlier

Kill the render function from compat and its uses. We no longer support
versions < 1.3