Introduce new operators for streaming filters len[e,g,ge,l,le]

These new operators can match depending the length of a field.
This way we can describe condition like: "filter for replies" because an annotation is reply when len(references) > 0
UserQueries structure change

- Added new field: description - user info about this notification
- Removed field type. We don't need general type any longer, we'll have user type only, with general filter