relax SVN archive

Some fix to add my last name...

Some copyright additions as usual for the users to know who contributed what...

Some obvious changes towards functional code for relaxation dispersion.

Next changes for the C modules will concern the 'real' code...

Added compiling of the relaxation dispersion C code as scons default and added dependency checks.

More work is needed, sucha as, obviously, the modification of the c code itself to suit relaxation
dispersion needs.

Corrected an error introduced in r8704 where the __init__.py file for system tests was modified for
the purpose of fast testing while coding...

Copied C files for Rx curve fitting for adapting as the code for dispersion curve fitting.

The new files will need a lot (!) of modifications to meet the needs of relaxation dispersion.

The commands used were:
svn cp maths_fns/relax_fit.h maths_fns/relax_disp.h
svn cp maths_fns/relax_fit.c maths_fns/relax_disp.c
svn cp maths_fns/exponential.h maths_fns/dispersion.h
svn cp maths_fns/exponential.c maths_fns/dispersion.c

Updated a few dosctrings and tried to improve the system test.

Started to implement the reading of 'r2eff' by relax_data.read() by first writing a system test.

Created a module for calculating different optimisation/energy potentials.

The function quad_pot() has been written to provide a flat-bottom potential.

Added a call to calc() to test the quadratic potential calculation.