Remove classes from aliases list

Eloquent and Seeder were used to extend from. Extending from aliases is a bad practice because it's hard to mock an none existing object when testing (see urls below) and you can't get any autocomplete from then in your IDE's. This lets us being less reliant on packages like this one: https://github.com/barryvdh/laravel-ide-helper  
Not that I'm saying it's a bad package. Just saying it's better to be less reliant.
 
The SoftDeletingTrait should be imported just like the UserTrait and the RemindableTrait. Same reasons as above.

PS: It's the same reason why I'd like to remove Str from this list. I'm not entirely sure atm what `FormRequest` is going to be used for but if it's in the same context as Eloquent and Seeder then it should be removed as well imo.