Bump dev version to 2.3.0

composer.json

 {
     "name": "doctrine/dbal",
-    "type": "library","version":"2.3.0-RC3",
+    "type": "library",
     "description": "Database Abstraction Layer",
     "keywords": ["dbal", "database", "persistence", "queryobject"],
     "homepage": "http://www.doctrine-project.org",

lib/Doctrine/DBAL/Version.php

@@ -36,7 +36,7 @@ class Version
     /**
      * Current Doctrine Version
      */
-    const VERSION = '2.3.0-RC3';
+    const VERSION = '2.3.0-DEV';
 
     /**
      * Compares a Doctrine version with the current one.