Add canaling of given query string on history rewind

When starting the flow or requesting the first step with a query string, it got lost. (E.g. `/flow/firstStep?foo=bar` redirected to `/flow/firstStep` *without* the query string). The losing of the query string was caused by a redirect without any parameters. Now added canaling of the query string into the redirect, e.g. `/flow?foo=bar redirects` to `/flow/firstStep?foo=bar` as well as `/flow/firstStep?foo=bar` to `/flow/firstStep?foo=bar`.