Workaround for a django bug that causes a "django.security.DisallowedModelAdminToField The field id cannot be referenced." when clicking on a raw_id_field referencing a MediaFile.

This should help for #552 until fixed django versions are released.
FeinCMS v1.10.1
Merge branch 'master' into next

* master:
  FeinCMS v1.10.1
  Workaround for a django bug that causes a "django.security.DisallowedModelAdminToField The field id cannot be referenced." when clicking on a raw_id_field referencing a MediaFile.

Conflicts:
	feincms/__init__.py