relax SVN archive

Import fixes by shifting to relax_io.write_spin_data_file().

Deleted the write_body(), write_header(), and write_line() functions from generic_fns.sequence.

This should accelerate the switch to relax_io.write_spin_data_file().

Wrote the relax_io.write_spin_data_file() function.

This writes spin specific data to a file (can be STDOUT). It will replace the write_header()
and write_body() functions of generic_fns.sequence.

Removed some unused imports.

More fixes for the test_read_peak_list_generic(). It now passes!

Rewrote the intensity_generic() function.

This is now much simpler (5 lines of code).

Fixes for the test_read_peak_list_generic() system test.

Complete redesign of the generic_fns.spectrum module.

This significantly simplifies the code base (much less jumping between functions) and prepares for
the generically formatted file support.

Added the new error class RelaxArgNotNoneError for when an argument should be None.

Commented out the header.