better fix for issue #2 and issue #6

- replaced ThreadLocal<MongoScope> and MongoScope implementation of ContextFactory Listener with MongoContext (created by MongoContextFactory)
- MongoContext holds a reference to a MongoScope and has getter and if-not-null setter method
- MongoAction implements ContextAction.run(Context) checking if the Context is a MongoContext, and if so then calling the MongoContext if-not-null setter method with the MongoAction.mongoScope member variable
- expanded constructWithoutNew.js test to include ObjectId(SOMEVALIDIDSTRING).getTimestamp() (reported failing by some)