[DX] Automatic registration of installed bundles

As discussed [here](https://github.com/symfony/symfony/issues/6082#issuecomment-51579210), this PR integrates the Wizard Bundle in the Standard Edition.

On each `composer require ...`, this library will:

1. check if the package is a bundle
2. convert the package name into a fully qualified classname (FCQN)
3. insert the FQCN in the `AppKernel` (if not already registered)

It depends on a Bundle which provides a the two following commands:

* `wizard:register:bundle`: registers the given FCQN in the `AppKernel` (useful when a bundle has been created manually)
* `wizard:register:package`: converts the given package name into a FCQN and registers it in the `AppKernel` (useful when a bundle has been unregistered, but is still installed, and needs to be enabled again)