Ability to set IPALLOC_RANGE via plugin-v2 configuration parameters

prog/net-plugin/config.json

@@ -74,6 +74,14 @@
           "value"
       ],
       "value": ""
+    },
+    {
+      "description": "The range of IP addresses used by Weave Net",
+      "name": "IPALLOC_RANGE",
+      "settable": [
+          "value"
+      ],
+      "value": ""
     }
   ],
   "network": {

site/plugin-v2.md

@@ -43,6 +43,9 @@ The parameters include:
   a larger size for better performance if your network supports jumbo
   frames - see [here](/site/using-weave/fastdp.md#mtu) for more
   details.
+* `IPALLOC_RANGE` - the range of IP addresses used by Weave Net and the subnet
+  they are placed in (CIDR format; default 10.32.0.0/12).
+  See [here](/site/using-weave/configuring-weave.md) for more details.
 
 Before setting any parameter, the plugin has to be disabled with: