Open _GlobalConfig for querying

Schema.js

@@ -75,6 +75,7 @@ function classNameIsValid(className) {
     className === '_Session' ||
     className === '_SCHEMA' || //TODO: remove this, as _SCHEMA is not a valid class name for storing Parse Objects.
     className === '_Role' ||
+    className === '_GlobalConfig' ||
     joinClassRegex.test(className) ||
     //Class names have the same constraints as field names, but also allow the previous additional names.
     fieldNameIsValid(className)