[5.6] Blade component aliases

[sebastiandedeyne]

This PR adds a component method to Blade for registering component aliases. Blade components are one of my favorite additions to Laravel, but the syntax can be quite verbose sometimes. This adds an easy way to create component directives, for components that you're going to use all over your app.

Blade::component('app.components.alert', 'alert');

@alert(['type' => 'danger'])
    @slot('title')
        Forbidden
    @endslot

    You are not allowed to access this resource!
@endalert

This PR also adds a shorter syntax, that assumes that you'll want to alias your component to the last part of the component path. This allows you to omit the second argument.

Blade::component('app.components.alert');

You lose explicitness though, so I could drop that from the PR if it's in the way.