MAGETWO-65026: Prepare code base for 2.0.15

Author: vzabaznov

composer.json

@@ -2,7 +2,7 @@
     "name": "magento/magento2ce",
     "description": "Magento 2 (Community Edition)",
     "type": "project",
-    "version": "2.0.13",
+    "version": "2.0.15",
     "license": [
         "OSL-3.0",
         "AFL-3.0"