feat(engine/history): log user task operations

- Introduce new User Operation Log logging operations
  performed by a user (such as "claim task")

- Populate Operation Log with Task Operations

- Deprecate TaskService.getTaskEvents(): evnets are now retreived
  from Operation Log instead of Comment Table

- Provide Query for operation log.

- Provide Sql migration scripts.

related to #CAM-1756, #CAM-1758, #CAM-1700