Add file transfer dialog
    
    This dialog will show the progress of files being transferred from the
    client to the guest and allows the user to cancel ongoing file transfer
    tasks.  The user can cancel each transfer individually, or cancel all
    ongoing transfers at once.
    
    Resolves: rhbz#1332180, rhbz#1324521
    Signed-off-by: Jonathon Jongsma <jjongsma@redhat.com>
    Acked-by: Fabiano Fidêncio <fidencio@redhat.com>