Post-registration "no login" option

[curiousyigit]

This PR adds the ability to register without login. This seems to be a pretty common need among users. The alternative being overriding the RegisteredController & route, this is a much more elegant solution.

Example usage:

// in config/fortify.php

    /*
    |--------------------------------------------------------------------------
    | Features
    |--------------------------------------------------------------------------
    |
    | Some of the Fortify features are optional. You may disable the features
    | by removing them from this array. You're free to only remove some of
    | these features or you can even remove all of these if you need to.
    |
    */

    'features' => [
        Features::registration([
            'login' => false,
        ]),
    ],

];

[taylorotwell]

Thanks for your pull request to Laravel!

Unfortunately, I'm going to delay merging this code for now. To preserve our ability to adequately maintain the framework, we need to be very careful regarding the amount of code we include.

If possible, please consider releasing your code as a package so that the community can still take advantage of your contributions!

If you feel absolutely certain that this code corrects a bug in the framework, please "@" mention me in a follow-up comment with further explanation so that GitHub will send me a notification of your response.