Fix bugs introduced by c3e48921d6

Avoid loosing stresses and make sure
the Castep regular expressions are
defined
Add a test for the Castep analysis script

Needs running by hand, but this is a start.

The test is expected to produce the elastic
constants found in the first coloumn of
Table 4 of my jadeite-diopside paper.
Add a test for the Castep setup script

This is expected to setup the strained input
files that can be used to calculate the first
coloumn of Table 4 of my jadeite-diopside manuscript.