[5.0] Extracted Contracts

Extracted Database, View, Validation, Translation and Queue contracts.

Fixed some typos along the way

Only ones remaining are:
* `Illuminate\Routing\Annotations\EndpointInterface`
* `Illuminate\Routing\Matching\ValidatorInterface`
That link you provided is not correct. This one is more up-to-date: https://github.com/phpDocumentor/fig-standards/blob/master/proposed/phpdoc.md.