How should it look like in the config? If we need to specify an absolute path, we won't be able to use `create-project` i.e., because you'd have to update your `composer.json` file in advance.

Moreover, for running a console application we need at least `id` and `basepath`, like:

    $config = array('id'=>'composer-console', 'basePath'=>$appPath);

Wouldn't it be OK to specify the config file relative to the project root? Like so:
```
{
  "extra": {
    "console-config": "config/console.php"
  }
}
```