Final fixes for bug #12735 (https://gna.org/bugs/index.php?12735).
The last problem was again triggered by the Scientific python PDB reader weirdness. Residues ending
in '+' were being treated by the PDB reader as a different molecule. But then the molecule names
LYS+, ARG+, etc. were causing problems as '+' was being treated as regular expression when matching
molecule names. Therefore the '+' character has been stripped from all molecule, residue, and atom
names.
