[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`
Is this better:
```php
// The Compiler engine requires an object that implements the Compiler
// contract, which in this case will be the Blade compiler, so we'll
// first create the compiler instance to pass into the engine so it
// can compile the views properly.
```