Fixes datetimepicker once and for all, fixes user model to return the culture not just the language, adds ability to localize the datetimepicker - will default to english but is easy to add other versions, currently the only custom one in there is brazilian (since it was already made).

fixes: U4-2863 Date picker-textbox jumps between 12 and 24 hours clock
U4-3537 Cannot clear date/time value, still have problems with it's null validation not clearing from the server