webui: adjust behavior of bounce url
    
    - bounce url param was renamed from 'redirect' to 'url'
    - support for 'delay' param added
    
    Behavior:
    
    - "Continue to next page" link is shown if 'url' is present
    - page is no longer automatically redirected if 'url' is present
    - automatic redirect is controlled by 'delay' param - it specifies
      number of seconds until redirection
    - info message 'You will be redirected in Xs' is show to notify
      the user that something will happen. It's useful even if delay
      is 0 or negative because redirection might be slow.
    - counter is decremented every second
    - delay is ignored if parsed as NaN
    
    https://fedorahosted.org/freeipa/ticket/4440
    
    Reviewed-By: Endi Sukma Dewata <edewata@redhat.com>