refactor(json): move object mapper generation

- configure ObjectMapper directly in the spin configuration object
- make spin configuration thread-safe
- reuse ObjectMapper according to
http://wiki.fasterxml.com/JacksonFAQThreadSafety
http://wiki.fasterxml.com/JacksonBestPracticesPerformance

related to CAM-2429
feat(json): write json nodes

- write to stream and writer

related to CAM-2429