Calendars demo

This is a simple example which demonstrates the capabilities of built-in calendar system. The calendar allows the Gantt to skip non-working days during calculation of task durations. By default the only non-working time in calendar are weekends.

Its possible to add the additional holidays or exceptions (working day which is on weekend). Holidays/exceptions should be represented as the `Gnt.model.CalendarDay` records in the calendar store.

Its also possible to apply custom styling for each holiday period.