set a db_type for ListField, SetField, and DictField, so subclasses don't have to define a new one
set a db_type for ListField, SetField, and DictField, so subclasses don't have to define a new one

sunils34/djangotoolbox,Knotis/djangotoolbox,kavdev/djangotoolbox,potatolondon/djangotoolbox-1-4,brstrat/djangotoolbox