Add date intervals as holidays

[GoogleCodeExporter]

Requested in issue #766: if enterprise is closed for a couple of weeks then 
adding all those days separately to the calendar is troublesome. It would be 
easier if there was a way to enter a range of days as holidays 

Original issue reported on code.google.com by dbarashev on 16 Jul 2014 at 10:33

[wlgrd]

any work on it?

[pierfrancesco72]

It is a pity that a button for recalculating the end date, also based on Day off periods, cannot be introduced.