Date/Time components improvements

[mkrause]

Some follow up items after #491.

• Allow DateInput to be editable rather than forcing the user to use the calendar picker
• DatePicker: allow changing the year/month more easily than navigating one month at a time

Also:

• useFloatingElement: Double check ARIA props (role/aria-) and keyboardInteractions logic
• useFloatingElement: Merge refs and styles into getReferenceProps and getFloatingProps?
• useFloatingElement: Add stories for multiple anchors on the same element.
• usePopover: Return anchorProps with a ref to get the source? Allows more flexibility: e.g. we can determine whether it is an SVG element