Allow edit of user on ticket-edit page

Previously, the user information could only be modified on the ticket-view
page. For instance, if creating a new ticket for a user, no new information
could be added or modified on the user until after the ticket was created

Fixes osTicket/osTicket-1.8#281
Merge pull request #291 from greezybacon/issue/281

Allow edit of user on ticket-edit page

Reviewed-By: Peter Rotich <peter@osticket.com>