User must specify verbose_name in ProcessedImageField constructor

[ghost]

Native Django ImageField __init__ method has verbose_name kwarg stated first explicitly which allows me to use it like that: ImageField("my image"). I think ImageKit should stay compatible with that style of model definition and add verbose_name explicitly too.

[vstoykov]

Not all fields in Django has verbose_name as first argument in order to be able to pass it as positional argument and not as keyword argument (like ForeignKey and others). At first it sounds tempting to make them similar but I'm afraid that even if it is not comfortable for new users, this can be a breaking change for old users. I do not have metrics about how many existing projects which depend on django-imagekit are passing processors as positional argument instead of keyword argument but still there is a possibility of that.