Proper autocomplete fix on user screen

autocomplete="off" no longer works on the latest browsers, chrome, and firefox have both disabled this feature recently.

However, I have found that clearing these fields with JavaScript works just as well.

When the new user dialog is opened (at the time the button is clicked), we clear all the form fields then.  When the button is clicked, this event actually triggers just before the modal opens, so it will be cleared when it is open.

Also, on page ready, clear all the password fields using JavaScript in a similar way (they should always be blank anyway)

I had to put ID's on fields of the new user dialog to find them using jQuery, but in order to not conflict with id's of other inputs on the page, I prepended them with "new_", for the new user dialog.

Finally, took out the autocomplete="off" attributes again, because they have no effect now anyway.