Use a custom redirect mechanism to workaround servlet container interference

Use a custom redirect mechanism to workaround servlet container interference

This mechanism bypasses the standard Wicket redirect mechanism because it
turns out that the servlet container reencodes Wicket's relative redirect urls.
This results in another way that parameters with forward-slashes can be borked.

Bad, bad servlet container.

org.eclipse.jetty.server.Response#L447: String path=uri.getDecodedPath();