In addition to accessing the properties, say, the radius,  with
atom.GetProp().radius, it is now possible to call atom.GetRadius().

Also, rename AtomBase::GetProp() to AtomBase::GetAtomProps().

git-svn-id: https://dng.biozentrum.unibas.ch/svn/openstructure/trunk@2114 5a81b35b-ba03-0410-adc8-b2c5c5119f08