Merge branch '4.4' into 5.1

* 4.4:
  Remove "version" from composer.json files, use "branch-version" instead

Author: nicolas-grekas

composer.json

@@ -26,5 +26,7 @@
         ]
     },
     "minimum-stability": "dev",
-    "version": "5.1.x-dev"
+    "extra": {
+        "branch-version": "5.1-dev"
+    }
 }