add api endpoint to stream job state updates and logs
The new endpoint is /api/v1/jobs/{id}/events shares the same implementation as `/aio/jobs/{id}/events', but with two differences:
- it returns a 'status' field (instead of 'state') to keep consistent with the other api calls
- authentication by token
Other changes in the PR:
- use line-delimited JSON stream instead of RFC7464 (because it is more common)
- fix regexes in urls.py
- allow streaming state changes only (without the logs)