make tcpv4-port configurable and add json schemas.

software/varnish/instance-varnish-input-schema.json

+{
+  "$schema": "http://json-schema.org/draft-04/schema#",
+  "extends": "./schema-definitions.json#",
+  "properties": {
+    "tcpv4-port": {
+      "allOf": [{
+        "$ref": "#/definitions/tcpv4port"
+      }, {
+        "description": "Start allocating ports at this value, going upward",
+        "default": 6001
+      }]
+    },
+    "backend-url": {
+      "description": "The backend url that varnish will cache",
+      "type": "string"
+    },
+    "web-checker-frontend-url": {
+      "description": "The entry-point-url that web checker will check the HTTP headers of all links in the web site",
+      "type": "string"
+    },
+    "web-checker-mail-address": {
+      "description": "Email address to which web checker result is sent",
+      "type": "string"
+    },
+    "web-checker-smtp-host": {
+      "description": "The smtp server to be used to send the web checker result",
+      "type": "string"
+    }
+  }
+}

software/varnish/instance-varnish-output-schema.json

+{
+  "$schema": "http://json-schema.org/draft-04/schema#",
+  "description": "Values returned by Varnish instanciation",
+  "properties": {
+    "url": {
+      "description": "Varnish HTTP service access information",
+      "type": "string"
+    }
+  },
+  "type": "object"
+}

software/varnish/instance-varnish.cfg.in

 {% set web_checker_parameter = slapparameter_dict['web-checker-mail-address'] -%}
+{% set tcpv4_port = slapparameter_dict.get('tcpv4_port', 6001) | int -%}
 [buildout]
 parts =
   publish-varnish-connection-information
@@ -17,7 +18,7 @@ develop-eggs-directory = {{ develop_eggs_directory }}
 offline = true
 
 [publish-varnish-connection-information]
-recipe = slapos.cookbook:publishurl
+recipe = slapos.cookbook:publish.serialised
 url = http://${varnish-instance:ip}:${varnish-instance:server-port}/
 
 [varnish-instance]
@@ -25,9 +26,9 @@ recipe = slapos.cookbook:generic.varnish
 
 # Network options
 ip = ${slap-network-information:local-ipv4}
-server-port = 6001
-manager-port = 6002
-stunnel-port = 6003
+server-port =  {{ tcpv4_port }}
+manager-port = {{ tcpv4_port + 1 }}
+stunnel-port = {{ tcpv4_port + 2}}
 
 # Paths: Running wrappers
 varnishd-wrapper = ${basedirectory:services}/varnishd