Upgrade to Groovy 2.4.7

Author: graemerocher

build.gradle

@@ -35,7 +35,7 @@ ext {
     datastoreVersion = "5.0.8.RELEASE"
     gantVersion = "1.9.6"
     gdocEngineVersion = "1.0.1"
-    groovyVersion = System.getenv('CI_GROOVY_VERSION') ?: "2.4.6"
+    groovyVersion = System.getenv('CI_GROOVY_VERSION') ?: "2.4.7"
     ivyVersion = "2.3.0"
     jansiVersion = "1.11"
     jlineVersion = "2.12"