untangle url methods

When trying to add a type hint I found that the two method signatures are so completely different that sharing the same method name should be avoided.

    Declaration of Cake\View\Helper\PaginatorHelper::url() should be compatible with
    Cake\View\Helper::url($url = NULL, $full = false)

The signature of PaginatorHelper::url() was:

    public function url(array $options = array(), $model = null)

Those are obviously two different things.

This also now allows to set $full true/false for url generation.