Kernel::Center_of_sphere_d

A model for this must provide:

template <class ForwardIterator>
Kernel::Point_d fo ( ForwardIterator first, ForwardIterator last)
computes the affine rank of the points in A = tuple [first,last).
Precondition: The objects are of the same dimension.
Requirement: The value type of ForwardIterator is Kernel::Point_d.