Imrpoves the datePicker on the add/edit userManager page 

Improves the look of the datePicker and does away with the button opening a datePicker in a new window.

This makes the following file redundant for THIS page. Is it used anywhere else??? If so point me to the pages and I will make the same changes so we can delete this file:

https://github.com/pfsense/pfsense/blob/master/usr/local/www/javascript/datetimepicker.js