[slim-skeleton-11.x] Adds Artisan::command(...)->... schedule methods

[nunomaduro]

This pull request continues the work on making the skeleton more "slim", by allowing to chain schedule methods directly on the Artisan::command call. Here is an example, on the console.php:

Artisan::command('inspire', function () {
    $this->comment(Inspiring::quote());
})->purpose('Display an inspiring quote')->hourly();

Optionally, users may also pass "arguments" to the closure command, my prefixing the schedule call to the schedule methods command:

Artisan::command('inspire {name}', function () {
    //
})->purpose('Display an inspiring quote')->schedule(['name' => 'taylor']->hourly();

If this pull request gets merged, here is the following pull request that adjusts this skeleton: laravel/laravel#6230.