Improve the way we get SPIP version (#2176)

* Improve the way we get SPIP version

This can be checked [here](http://www.lentrepot.fr/)

* Fix a typo

src/apps.json

@@ -8397,7 +8397,8 @@
         1
       ],
       "headers": {
-        "X-Spip-Cache": ""
+        "X-Spip-Cache": "",
+        "Composed-By": "SPIP ([\\d.]+) @\\;version:\\1"
       },
       "icon": "SPIP.png",
       "implies": "PHP",