Console

A helper class that let's the user control the game remotely.
Currently it supports these commands: "fps on", "fps off", "scene graph", "help", "exit".

But it is easy to add new commands without modifying the cocos2d code.

It also adds a helper function in Scheduler that lets you run an `std::function<void()>` in the cocos2d thread.

Use cases:
- It can use for realtime debugging (useful for the new renderer)
- for QA automation