Create MARC data elements specific to Zentralbibliothek Zürich

[pkiraly]

[pkiraly]

@zb-saml I incorporated your code, thanks a lot for the contribution!

One imporant note: you created a local 035 field, with a single subfield, however you also added this subfield to the MARC21 definition. In this form the local ZB related 035 override the definition of the core, so all not other subfields will be taken as invalid. If this is the intention, than we are ready. If you just want to add this subfield we should remove the locally defined 035 class.