Clusterization and tree building

Files
file	bounding_box.hpp
	Implementation of class NiHu::fmm::bounding_box.
file	cluster.hpp
	implementation of class NiHu::fmm::cluster_base
file	cluster_tree.hpp
	Implementation of class NiHu::fmm::cluster_tree.
file	divide.hpp
	Cluster division strategies.
file	elem_center_iterator.hpp
	Classes for iterating through elements and fields.
file	empty_cluster.hpp
	Definition of the class empty_cluster.
file	lists.hpp
	Definition of class NiHu::fmm::interaction_lists.

Detailed Description