relax SVN archive

Wrote spin_id_to_data_list() to convert a single spin ID into a list of mol, res, and spin names and numbers.

The relax_io.read_spin_data_file() function now calls generic_fns.sequence.validate_sequence().

This is a more advanced check of the sequence information. The validate_sequence() function has
also been modified to handle single data lines.

Bug fix for the relax_io.read_spin_data_file() function.

The column number check was incorrect due to the column renumbering.

Added the missing import of relax_io.read_spin_data_file().

Converted spectrum.read_intensities() to use the new relax_io.read_spin_data_file() function.

This is only for the generic formatted file.

Docstring modification better explaining spin_id.

Converted value.read() to use the new relax_io.read_spin_data_file() function.

This converts the user function to the 1.3 line design as well.

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().