chore(spin): add spin engine plugin

- changes the way spin is integrated into the engine: instead of
  the engine actively looking for spin, it now is registered as a process
  engine plugin
- decouples engine and spin

related to CAM-2966
refactor(spin): extract DomXmlDataformat and JacksonJsonDataformat

- introduces separate maven projects for these data format implementations
- keeps the XML and DOM API interfaces in the core project

related to CAM-2966