More flexible predicate for interceptors

[Diokuz]

The case: mock a request, which have no applicationId query parameter.

Probably, teremock should support functional predicates, e.g.

const interceptor = {
  url: 'example.com',
  predicate({ query, url }) {
    return !query.applicationId
  }
}

[boris-chernysh]

I would also like to add a predicate by body

[anru]

#27 issue is related also