feat(engine): add set variable from serialized to task service

related to CAM-2544
chore(engine): add interface for variable type specifications

- allows potential extensibility by custom variable types
- adds missing license headers

related to CAM-2544
refactor(engine): allow different spin formats for spin variable type

- enables to store some variables in one format and others in a different
  format
- has one default format that is used when setVariable(name, value) is used

related to CAM-2544