event excludes now sorts and filters
add datepicker and modify nus date style

Datepicker API:
datepicker.register(clicked_jquery_object, appendto_jquery_object, date_callback, select_callback)

where clicked_jquery_object is the element that triggers the datepicker,
appendto_jquery_object the element where the datepicker is positioned relative to,
date_callback a function that returns the current selected date for the datepicker,
select_callback a function that runs when a date is selected in the datepicker.