added ScrollCalendar.setDateRange()

[eldad-eg]

I wasn't sure if the new constructors for ScrollCalendarAdapter, DefaultRangeScrollCalendarAdapter, and DefaultDateScrollCalendarAdapter should replace the current ones.

Is the addCurrentMonth attribute overkill? Is it fine to just add it automatically, and remove it if setDateRange() is called?

Idea for future improvement: explicitly specify the initial month.