Shifted the focus of the Grace module from residues to spins.
Fixed the calls to x_return_value() and y_return_value().
Fixed the call to get_data().
Removed a remaining instance of 'self' from the write() function.
Fixed the grace.write() user function interface.
A few small fixes for the write() function.
Updated the grace.write() user function interface to the new design.
Converted the Grace write() function to the new design.
The pipe argument is now optional for RelaxNoSimError.
Converted the 4 write_*() functions to the new design.