relax SVN archive

Converted all structural object methods to use the selection object rather that atom ID strings.

This should have a significant impact on the speed of certain operations within relax. The most
obvious effect will be a huge speed up of the interatom.define user function. There should be speed
ups with a number of other user functions relating to structural information. All parts of relax
have been updated for the change.

Created the structural object Internal_selection.mol_loop() method.

This is to simply quickly loop over all molecule indices of the selection object.

Converted the rotate() and translate() structural object methods to use the new selection object.

The atom_id arguments have been replaced with selection arguments. Therefore all parts of relax
which call these methods must first call selection() to obtain the Internal_selection instance.

Fixes for the new structural object Internal_selection object.

The atom indices are not stored via the molecule index.

Indentation fix for the internal structural object validate_model() method.

Missing import of the Internal_selection class.

The internal structural object validate_models() method now accepts the verbosity argument.

This is used to silence printouts.

Added the selection() method to the internal structural object.

This parses the atom ID string using the lib.selection module, loops over the molecules and atoms,
performs matches using re.search() via lib.selection, and populates and returns the new
Internal_selection object. This can be used to pre-process the atom ID string to save huge amounts
of time.

Created a special internal structural object selection object.

This will be used for massively speeding up the internal structural object. The use of the
lib.selection module by the internal structural object is currently very slow as a huge number of
calls to re.search() are required. The idea is to avoid this by using lib.selection once to
populate this new selection object, and then reusing this object to loop over molecules and atoms.

Implemented the frame_order.simulate user function backend for the double rotor frame order model.

This involved extending the algorithm to loop over N states, where N=2 for the double rotor and N=1
for all other models. To handle the rotations being about the x and y-axes, an axis permutation
algorithm is used to shift these axes to z prior to decomposing to the torsion-tilt angles. The
reverse permutation is used to shift the axes back after correcting for being outside of the allowed
angles.