[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`
Yes - laravel doesn't follow those though, as I said. Laravel has it's own standards.

Regarding its definition, you quoted it: `the user should not rely on any retrieved value`. That's exactly what it means.