relax SVN archive

Removal of a few unused imports.

Docstring fix for the read() function.

This is the PCS, not RDC.

Fix for the RDC and PCS display() and write() user functions for when no errors exist.

Added a call to pcs.display() in the DNA PCS system test.

This is to test out the operation of this user function.

Clean up of the RDC and PCS modules.

All the residual code from the relax_data module has been eliminated.

Added 2 system tests for alignment tensor optimisation using DNA PCS data.

Wrote the back end for the pcs.display() and pcs.write() user functions.

Wrote the back end for the rdc.display() and rdc.write() user functions.

Fix for the molmol.clear_history() user function.

This was calling the non-existent self.__relax__ structure.

Fix for 3 of the 'value' user functions.

These were calling the non-existent self.__relax__.