Std:string and QString

Hi,

I hit this issue again today and Geoff mentioned he had hit it before.
Converting an std::string to a QString. The label engine does it and now the
ribbon engine needs to in order to figure out which are the CA atoms in the
residues.

I think the simplest and most efficient way of converting them is as I did in
the ribbons engine or the label engine,

QString atomID = QString(r->GetAtomID(&*a).c_str());

The string is then converted and other operations can be performed. Geoff was
saying that Qt can optionally be compiled with support for std::string but I
don’t think we can rely on this. If there is a better way to get the
std::strings in then it would be good to settle on one method and use it
consistently - otherwise I would suggest the std::string::c_str() is the best
candidate.

Thanks,

Marcus