relax SVN archive

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.

Clean up of the MF_split_grid_memo.__init__() method.

This now matches MF_memo, but with a few additional variable initialisations (not all may be needed
in the end).

Only the minimal amount of info is being passed into MF_split_grid_memo.

The other info can be passed in through a command.store_data() call. This mimics the current
MF_memo operation.

Renamed MF_super_grid_memo to MF_split_grid_memo.

This is the memo for the parallelised grid!