problems with "reveal" option of hbonds, contacts, clashes

[Elaine Meng]

In "hbonds", this option should show the whole residue with an H-bonding atom if that residue is nonpolymer (e.g. water, ligand). Currently shows none of that residue. Probably occurred when implementing considering polymer residues as two parts, sidechain and backbone.

Conversely, the consideration of polymer residues as two parts does not seem to be implemented in "contacts/clashes"... thus that command also does not have the problem of not showing nonpolymer residues.

[Eric Pettersen]

In both hbonds and clashes/contacts, backbone wasn't handled right because I didn't realize that atom.is_backbone is a function call, not a property (and therefore needs to be atom.is_backbone()). Also, clashes/contacts weren't revealing the entirety of non-polymer residues, just the clashing/contacting atoms.