relax SVN archive

Fix for the call to write_xy_header().

This is now independent of the number of data sets, and is called correctly.

Deletion of the write_header() function.

This is now redundant due to the improvements in write_xy_header().

Added symbol formatting to the individual graph sets in write_xy_header().

Bug fix for write_xy_header(), a statement typo was stopping relax from running.

More changes to write_xy_header().

The return_units() and return_grace_string() analysis specific methods are no longer passed in as
args but are set up in the method itself. Many simplifications have been made. And now spin data
has been made axis independent - it can be X or Y data.

write_xy_header() now has a sets arg for specifying the number of data sets in the graph G0.

Clean up of write_xy_header().

Labels are now not overwritten if supplied, all file.write() operations are collected together, and
the X and Y-axis settings have been merged.

Converted write_multi_header() to write_xy_header() and simplified the args by expecting [X, Y] pairs.

MF_grid_memo is being used to for the parallel grid sub-elements.

This was how the original code worked, not sure why this changed?

The MF_split_grid_command.store_data() method is being used to pump in all the data.

This comes from the base class.