Centralizes list of system classes into Schema

src/RestQuery.js

@@ -1,6 +1,7 @@
 // An object that encapsulates everything we need to run a 'find'
 // operation, encoded in the REST API format.
 
+var Schema = require('./Schema');
 var Parse = require('parse/node').Parse;
 
 import { default as FilesController } from './Controllers/FilesController';
@@ -171,7 +172,7 @@ RestQuery.prototype.redirectClassNameForKey = function() {
 
 // Validates this operation against the allowClientClassCreation config.
 RestQuery.prototype.validateClientClassCreation = function() {
-  let sysClass = ['_User', '_Installation', '_Role', '_Session', '_Product'];
+  let sysClass = Schema.systemClasses;
   if (this.config.allowClientClassCreation === false && !this.auth.isMaster
       && sysClass.indexOf(this.className) === -1) {
     return this.config.database.collectionExists(this.className).then((hasClass) => {
@@ -423,7 +424,7 @@ RestQuery.prototype.handleInclude = function() {
     this.include = this.include.slice(1);
     return this.handleInclude();
   }
-  
+
   return pathResponse;
 };