relax SVN archive

Renamed the main model-free module.

The original module was specific_fns.model_free.model_free whereas the new is
specific_fns.model_free.main.

Numeric to numpy conversion.

Added a missing import.

Added an empty package __init__ module.

Added a directory for unit tests of the model-free specific code.

Added an empty package __init__ module.

Directory rename.

Removed the recently added _opendx directory (it already exists as _dx).

Added the missing relax base directories to the unit tests.

Deletion of the 'minimise' relax package.

This package has been replaced by the minfx python package (which is derived from the 'minimise'
code).