Change month dropdown display in date pickers to include month number

[jane]

For those people who have trouble converting numerical dates to text month names, let's amend the date picker month dropdown to include the month number as well, credit card form style.

01-Jan
02-Feb
03-Mar etc.

[azaozz]

In [18860]:

Change month dropdown display in date pickers to include month number, fixes #18838

[nacin]

Internationalized in [19820].