shifter debug info

This PR will introduce more granularity to control the shifter output. By default, if node is running in debug mode, shifter will do so as well, and on top of that, you can control specific settings by using some helper options for `lint`, `coverage`, `silence` and `quiet`, here is an example:

```
    var plugin = app.yui.plugin({
        registerGroup: true,
        registerServerModules: true,
        useServerModules: true,
        lint: true,
        coverage: true,
        silence: false
    });
```