refactor RSP using BaseParty fragment

[matt-beanland]

relies on diffo-dev/diffo#81

[matt-beanland]

we've done RSP using BaseParty fragment. We chose not to use partyDSL etc PartyRef to relate the RSP and Instances, instead the relationships are implicit using rsp_id property which carries the epid.

Probably should have used the short_name, but it is an atom property used for authentication and don't think AshNeo4j supports an atom primary key, so we decided that in diffo for now.