TISTUD-5079 Make JSCA handling forgiving of arbitrary new properties

TISTUD-5079 Make JSCA handling forgiving of arbitrary new properties
      - Try to just parse as JSON and de-serialize the JSON into model objects (without intermediate step of using a schema and transitioning between expected states)
      - Clean up code
      - Use collections over arrays in API
      - handle difference in property name between JSCA and serialization for isInternal
      - remove old JSCA handling code