re-enabled query cache of ringo-sqlstore

see https://groups.google.com/d/msg/ringojs/Ji7BFWyODYQ/s_mb9hIY9pcJ resp. https://github.com/TechEmpower/FrameworkBenchmarks/issues/289#issuecomment-20669224 for an explanation of what the query cache does.

ringojs-convenient/app/models.js

@@ -17,7 +17,7 @@ var store = exports.store = new Store(connectionPool);
 var queryCache = module.singleton("queryCache", function() {
     return new Cache(10000);
 });
-//store.setQueryCache(queryCache);
+store.setQueryCache(queryCache);
 
 // define entities in DB
 exports.World = store.defineEntity('World', {