[Tagging] Unmarked opening hours

[Michał Brzozowski]

In the course of surveys, I fill in opening_hours of shops and other
venues. Sometimes though, they are not marked outside. Therefore, when
looking at a feature that lacks opening_hours other mappers and I
can't tell the reason. I've been thinking of a standardized way of
marking such cases, like:
opening_hours:status=unmarked
which is to be understood that mapper didn't see opening hours
displayed outside (but other sources may be available).
This would benefit survey planning. A mapper will know to come at
standard business hours to ask staff and that it can take slightly
more time to survey.

Michał