Module grafen::system

This module implements the basic structures of an atomic system.

A final System consists of a set of Residues, which can be moved around and translated with ease. Each Residue in turn consists of some Atoms. These atoms have positions relative to their parent.

This somewhat convoluted structure is inherited from molecular simulation packages in which atoms are commonly grouped as such. A proper physical way to look at is that atoms can be similarly grouped into molecules.

Structs

Atom	Every atom in a residue has their own code and relative position some base coordinate.
Coord	A three-dimensional coordinate.
Residue	Every residue has a name and a list of atoms that belong to it with their relative base coordinates. The names are static since they are generated only once from a single source.
ResidueBase	A base for generating atoms belonging to a residue.
System	A finalized atomic system which consists of a list of residues, each of which contains some atoms.