Metadata import

now instantiating both works and instances from data coming from aleph.

unfortunately i have to implement some elements for the whole chain aleph -> marc21 -> mods -> hel

Obviously, you're right. A sediment from a piece of cut and paste programming.  I've set it to the empty string, and modified the work datastream such that 
 xml.titleType { xml.text(type) } unless type.blank?
since the normal case is that there shouldn't be a titleType (unless it its one of the four exceptions to the rule)