Throw error if pagination amount <= 0 is requested

[spawnia]

Related Issue/Intent

Resolves #760

Changes

This prevents an issue where Laravel defaulted to the Model's $perPage amount when a user
requested a count of 0. The paginate_max_amount setting was ignored in this case.

Now, if a client tries to request a paginated field with an amount of <= 0, they will be met with an error:

Requested pagination amount must be more than 0, got 0.

To make this change easier and apply consistent behaviour to all paginated fields (@paginate and @hasMany), i refactored some parts around how the pagination arguments are handled.

Breaking changes

Nope

[chrissm79]

Great job @spawnia, thanks!!

[zjbarg]

That was fast, you guys are awesome, thank you. @spawnia