Update article&timespan param of segment blueprint
Update article&timespan param of segment blueprint

Changes:

- `_article` renamed to `is_article`,
- `timespan` type changed to `datetime` (interval was removed from
  agreeed blueprint).

remp/crm#258

remp2020/remp,remp2020/remp,remp2020/remp,remp2020/remp,remp2020/remp