MISC-4: Build custom error pages

Have configured a basic notification page for tor2web pages, but because NGinx is being a pain, it doesn't really return an appropriate status code. Currently it'll 301 the visitor to a page called 405.html which details why the request was blocked.

For some reason, NGinx seems to be quite determined not to use custom error pages for 405/406 etc, will come back and look at sorting that out later. For now the config in place is

    error_page 405 = /405.html; # This has no impact currently
    location /405.html {
        root /usr/share/nginx/onions/bentaskercouk;
    }

    if ($http_x_tor2web){
        set $tor2web T;
    }


    # Avoid redirect loops
    if ($request_uri = '/405.html'){
        set $tor2web R;
    }

    if ($tor2web = T){
        return 301 /405.html;
    }

Will get the 50x error page built a little later