relax SVN archive

Fixes for solely specifying that the paramag centre will be optimised.

Activated the paramag centre finding system test.

This currently fails as the code to do this does not exist.

Fixes for the system tests for the pcs.centre() to paramag.centre() shift.

The paramag user function class is now accessible.

A few fixes for the paramag prompt code for the change from the PCS.

The fix flag is now accepted by the paramag.centre() user function.

Renamed the pcs.centre() user function to paramag.centre() to abstract for the PRE.

The paramagnetic centre is shared between different NMR interactions, so this function has been
abstracted and is no longer PCS dependent.

Renamed the pcs.centre() user function to paramag.centre() in the system tests.

This is because in the future this paramagnetic centre position is shared with the PRE.

Added a new system test for the direct optimisation of the paramagnetic centre.

Better support for RDC and PCS correlation plots with and without errors.