Minor change to voronoi sheet example.
Added reading capability to xyz reader writer, needs more testing.
Working Xyz reader and writer.  Unified use of title line in xyz and res reader writers.  Added bunch of tests as well.
Changed voronoi slab region ordered basis to look for species around a vertex
before placing an atom to see if it can continue the pattern.
Fixed error in saving outcome of castep run, used wrong castep file name.