Utility for building WebSockets URLs from a given spec.

The spec may be an url string or an object defining the url properties
(host, port, service name and a query string).
A test page for the WebSocket url builder utility.
Check url strings for the right protocol-prefix.

For WebSockets 'ws://' is required as a prefix.
Changed text of error messages.
Added script tag for 'WsURLBuilder' to test/demo pages.
Pass a connection spec instead of host, port and service name.
Upadted test/demo pages to be compliant with the modified signatures of the
constructor functions for WebSocket connection and client.