relax SVN archive

Fixed a call to the structural PDB writer.

Fixed some more calls to the structural method atom_add().

Typo bug fix for another call to the structural method atom_add().

Fixed a call to atom_add().

Added a RelaxError for when the PDB MODEL record is corrupted.

The RDC and PCS error data structures are now properly handled and setup in __init__().

The RDC and PCS errors data structures are now created by the __minimise_setup_*() methods.

These are also passed into the minimisation code.

Try 2: PCS errors in a file separate from the data can now be read.

This matches the changes for the RDC at r7202, and is what r7204 should have been.

Reverted the last revision, r7204, as this included too much.

The command used was:
svn merge -r7204:7203 .

PCS errors in a file separate from the data can now be read.

This matches the changes for the RDC at r7202.