added missing composer config for the portal's composer.json

- php 5.6+
 - dump the autoloader as optimized as possible

datamodels/2.x/itop-portal-base/portal/composer.json

@@ -1,5 +1,12 @@
 {
 	"license": "AGPLv3",
+    "config": {
+      "platform": {
+        "php": "5.6.0"
+      },
+      "sort-packages": true,
+      "classmap-authoritative": true
+    },
 	"autoload": {
 		"psr-4": {
 			"Combodo\\iTop\\Portal\\": "src/"