Create and return a L{BBRefTargetDirective} subclass.

def make_ref_target_directive(ref_type, indextemplates=None, **kwargs):
    """
    Create and return a L{BBRefTargetDirective} subclass.
    """
    class_vars = dict(ref_type=ref_type, indextemplates=indextemplates)
    class_vars.update(kwargs)
    return type("BB%sRefTargetDirective" % (ref_type.capitalize(),),
                (BBRefTargetDirective,), class_vars)