DatePicker and Calendar updates

[mark-tate]

• Calendar now supports children, enabling you to compose Calendars from CalendarNavigation, CalendarWeekHeader and CalendarDateGrid
• renamed CalendarCarousel to CalendarDateGrid
• better support for rest so that it passes to the root element in each component
• hooks are only passed values they support
• switched date format in examples to all use DD MMM YYYY
• DatePicker examples with US locale, can now parse dates with or without a comma
• updated docs with API changes