relax SVN archive

Reverted r19410 as this does not preserve svn history.

The command used was:
svn merge -r19410:r19409 .

Restored the old http://www.nmr-relax.com/api/1.2 and http://www.nmr-relax.com/api/1.3 directories.

The commands used were:
svn copy svn+ssh://bugman@.../svn/relax/website/api/1.2@r15476 .
svn copy svn+ssh://bugman@.../svn/relax/website/api/1.3@r15476 .

The reason is because there are many old links in the relax trackers and mailing list archives to
these API HTML pages and therefore it would be good that these are preserved. One idea would be to
have separate directories for each major relax version number, as this documentation varies hugely
between these version numbers and hence links are not preserved.

Restored the default behaviour of the spin_loop().

The skip_desel flag is now functional and defaults to False.

Fix for the analysis specific API common _return_value_general() method.

The value of None is now handled properly when a simulation value is asked for.

Fix for the new pipe_control.mol_res_spin.count_max_spins_per_residue() function.

The data pipe container was missing.

Added the skip_desel flag to the important pipe_control.mol_res_spin.spin_loop() generator function.

This is used to skip deselected spins within the loop. As must of the code in relax using the
spin_loop() does this anyway, this can be used to simplify many of the spin looping elements in
relax.

Updated the pipe_control.plotting.determine_functions() function.

Fixes for the change of the grace.write user function data type 'spin' to 'res_num'.

Created the pipe_control.mol_res_spin.count_max_spins_per_residue() function.

This will be used by the plotting module to determine if more than one spin per residue exists.

The grace.write user function data type argument sequence values have changed.

Instead of 'spin', this can now be 'res_num' or 'spin_num' to specify that either the residue number
or spin number should be plotted on the desired axis. The x_data_type now defaults to 'res_num'.