schema/oparl:Organization: fix naming

Our frozen schema version still call the name field nameLong. So we use
this everywhere.
schema/oparl:System: fix naming

The reference to the list of bodies is called "bodies" in our frozen
schema version.
tests/test_schema: fix typo
testdata: fix json syntax
testdata: meeting also requires participant
testdata: fix consultation sample
testdata: list references should be arrays
testdata/membership: add required @{context,type,id}
tests/test_crawler: use correct URL

While serving "oparl.example.org" with a simple server on localhost we
have to replace the host before requesting each URL. This is done by
overriding the retrieve method of the Crawler.