$Header$

This directory contains directories referred to as 'arrangements'.
Each arrangement contains further directories holding the 'thorns'.

The build system searches for thorns and creates a 'ThornList' in 
a configuration's directory configs/<configuration-name> where
all configuration-specific files are kept.  This thorn list
can subsequently be hand-edited.

In any compiled Cactus executable all thorns must have unique names.
This implies that each thorn should appear in one, and only one,
arrangement.