Updating calendar pieform element to use datepicker/timepicker

(Bug #1267239)

The datepicker is now keyboard accessible but not fully screenreader
accessible - but the folks at datepicker are working on that

The key bindings you need to know for datepicker:
PAGE UP: Move to the previous month.
PAGE DOWN: Move to the next month.
CTRL+PAGE UP: Move to the previous year.
CTRL+PAGE DOWN: Move to the next year.
CTRL+HOME: Move to the current month. Open the datepicker if closed.
CTRL+LEFT: Move to the previous day.
CTRL+RIGHT: Move to the next day.
CTRL+UP: Move to the previous week.
CTRL+DOWN: Move the next week.
ENTER: Select the focused date.
ESC: Close the datepicker

The key bindings added for timepicker:
(to avoid clashes with existing key bindings)
ALT+UP: Move hour slider up one step
ALT+DOWN: Move hour slider down one step
SHIFT+LEFT: Move minute slider down one step
SHIFT+RIGHT: Move minute slider up one step

Also added the prev/next year button options

Change-Id: Iff857ba9efb23fd123de6af8f78ceffee9c0ac79
Signed-off-by: Robert Lyon <robertl@catalyst.net.nz>