relax SVN archive

Added a check to see if the file is empty to read_spin_data_file().

Fixed the calls to rdc.read() and pcs.read() in the system tests.

Fixes for the unit tests of generic_fns.mol_res_spin.generate_spin_id_data_array().

Modified generic_fns.rdc.read() to use the new relax_io.read_spin_data_file().

Modified generate_spin_id_data_array() so that column numbering starts at 1.

Created the read_spin_data_file() generator function.

This is designed to replace quite a few inconsistent functions throughout the generic function code
base. It reads a columnar formatted file with a spin per line.

Fixed the call from the prompt to the generic fns.

Changes to the pcs.read() and rdc.read() user function interfaces.

Columns are now numbered from 1 - note this will break many things! The spin_id_col is now accepted
and the spin_id arg is explained.

The docstrings have also been modified all over these user function classes to replace
'identification string' with 'ID string'.

Removed some empty lines.

Added the spin_id_col arg to the rdc.read() user function.

This allows 2 different formats for spin identification - spin ID string or mol name, res name and
num, and spin name and num.