Add support for freeform number entry to SC.DateFieldView

Here is my work to solve the issue #783.
This patch keep the actual way that SC.DateFieldView work and add
support for freeform number entry.
You still have to navigate between sub-fields but you can now press
numbers to change the value of the date or time. If the pressed number
create an impossible date, (example: 25 hours), the value will not be
updated.
Add support for: %Y, %y, %m, %d, %H, %I, %M, %S