Support for Logical keywords

[tl-madhulika-mitra]

As per pactflow docs - allOf keyword is called out as not being supported due to Json Schema issues. But are none of the keywords supported like OneOf/AnyOf - since a lot of our apis see false negatives as their response structures have oneOf in them.

[mefellows]

We do support both oneOf and anyOf, and technically we support allOf (just with the caveats that the schema testing follows JSON schema rules). The work around is suggested in #14 and seems to work most of the time for that case.

I've added a few examples of how logical keywords are currently supported for common use cases here: https://github.com/pactflow/example-bdct-logical-keywords