[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`
BTW, I made `DatabaseQueue::release()` an int because it returns `DatabaseQueue::pushToDatabase()` which returns an int (`insertGetId()`).