DateChooser firstDayOfWeek is non functional

Most countries don't use Sunday as the first day of the week. Only USA, Canada, Japan and a few other do so. Setting the day of the week to be Monday like so doesn't seem to have any effect.

`model.firstDayOfWeek = 1;`

Looking at the setter it seems to me that it should be calling updateCalendar() (which it isn't) and perhaps changing model.dayNames to reflect the new order.

Even when dayName array is modified and updateCalendar is called manually there is still no effect. It looks like updateCalendar is missing code to take into account the first day of the week.

Start by tracing the DateChooser firstDayOfWeek setter and updateCalendar() to reproduce why changing the value does not affect the calendar. Check how model.dayNames is used when the calendar is rebuilt; done means Monday-first configuration changes the displayed week order and works with the reported model.firstDayOfWeek = 1 case.

Written by the indexing model from the issue text.