TSphinxWebLogin: Add LogoutAndEndSession overload with post_logout_redirect_uri support

[wlandgraf (Wagner Landgraf)]

@Owen_Dearman

Also note that the post-logout redirect URI has been added to SphinxClientApp.PostLogoutRedirectUris for validation. Is there a better way of implementing this behaviour, please?

I didn't understand your comment here.

Other than this, yes, it's a valid suggestion, but maybe just make the Client property public? With it, you can just build an call the logout url the way you want to.