Help text for arguments

[morgante]

Currently, when using custom filtersets to add additional arguments to a query there does not seem to be any way to change the automatic description. Instead, the description is always "Filter" for any arguments.

It would be good to offer a way to change this, ideally by picking up on the label argument of the Django filter, like this:

class OutcodeFilter(django_filters.FilterSet):
    class Meta:
        model = Outcode
        order_by = ('code', )

    max_time = django_filters.NumberFilter(method='filter_max_time', label="The maximum time")
    def filter_max_time(self, queryset, name, value):
        return queryset.max_time(value)