Allows use of an array of date formats

Moment.js allows use of an array of date formats when parsing dates.

This means that you can do... `moment('05/05/1945', ['dd/mm/yyyy', 'dd-mm-yyy'])` and `moment('05-05-1945', ['dd/mm/yyyy', 'dd-mm-yyy'])` and both will work. Moment will keep trying the formats in the array until it finds the correct one to parse it with.

I have updated the date picker to accept an array for the 'format' parameter. It then uses the first format in the array as the display format.
Right, I propose adding a global setting to enable/disable strict parsing for the date picker. I believe my issue of `moment("05/05/45", ["DD/MM/YYYY", "DD/MM/YY"])` returning "05/05/0045" rather than "05/05/2045" is actually an issue with moment.

What do you think to this solution?

I have opened an issue with moment for the format array parsing order https://github.com/moment/moment/issues/1746