[5.0] Adding array_whitelist() and array_blacklist() functions

check if a value is whitelisted or blacklisted
useful for double checking url parameters like filters & sorts

Example: 
```php

/* Controller index */
public function index($sortBy = 'name')
{
    $sortBy = array_whitelist($sortBy, ['name', 'age', 'rank'], 'name');

    // ...
}

```
The short description must end in a full stop.