relax SVN archive

Refinement of the dipole_pair user function definitions.

Created the dipole_pair.unit_vectors user function definition.

Created the backend of the dipole_pair.read_dist user function.

Created the dipole_pair.read_dist user function definitions.

This new user function is for simplifying the loading of many different interatomic distances into
relax.

Fix for the dipole_pair.define user function - the interatom object can pre-exist, containing other data.

More refinements of the dipole_pair.define user function definition.

Refinement of the dipole_pair user function definitions.

Created a set of icons for the dipole_pair user functions.

Shifted the relax_data.dipole_pair user function into the new dipole_pair user function class.

This has also been split into two new user functions:
dipole_pair.define used to set up the magnetic dipole-dipole interactions.
dipole_pair.set_dist used to set up the r^-3 averaged interatomic distances.

The relax_data.dipole_pair backend now uses the direct_bond flag.