Improve "days (until store closing)" duration behaviour

Previously the "days (until store closing)" duration type would not count the first day, if the store was closed on the start day of the booking. This has been changed so that when starting an "days (until store closing)" on a day when the store is closed, the first day is always counted. This does not change the behaviour in case the store IS open on the start day, but the booking is started after the closing time (in this case, the first day is not counted)