Allow staff to cancel user lookup popup when creating a new ticket

The change will allows staff to open a new ticket without going through the
"forced" user lookup popup. On cancel the staff is presented with a
simplified user info form with email and name being the only fields
required.
Merge pull request #434 from protich/feature/new-ticket-revisited

Allow staff to cancel user lookup popup when creating a new ticket

Reviewed-By: Jared Hancock <jared@osticket.com>