add some instance specs and ...

[ndushay]

also:

• remove a few more zs elements from LC fixture data
• add rdfxml and ttl for LoC instance examples
• add a few specs to work_related_work_5xx_spec
• redo dir structure for top level stanford fixture data

@jgreben

[ndushay]

Josh: sorry this is so big. Ignore all the fixture data stuff and scroll waaaay down to spec/instances to see my stuff.

If you want, I can break the fixture data changes into a separate PR from the spec changes.