Update UKLP harvesters

[amercader]

Three small changes:

• Set Resource type to None instead of 'Undefined'
• Set extra 'UKLP' = True instead of 'INSPIRE' = True

These two changes will require manual update of the database.

• Allow datasets to be updated if the old source is inactive, even if the metadata date hasn't changed:

    if last_harvested_object.metadata_modified_date is None \
       or last_harvested_object.metadata_modified_date < self.obj.metadata_modified_date \
       or self.force_import \
       or last_harvested_object.metadata_modified_date == self.obj.metadata_modified_date and last_harvested_object.source.active is False: