This allows us to see the whole spec at once and fix a bug w/ custom registry definitions

...in json-schema. Also removes the leading `:` which the definitions keys also didn't have. This allows the refs and definitions keys to match and be standards-compliant.

Perhaps this really needs to be fixed at a lower level, but I noticed that at times I was getting definitions whose values where just refs back to the same definition. These seemed to come in addition to the correct result that had the actual definition in it. So this just filters out the circular ones.

...in json-schema-test/references-test. Fix was in 23488b2.

...including one commented-out failing test that should pass once issue metosin#464 is fixed.