Return coordinate information with Bpform.get_structure

[jonrkarr]

Done. Returns 3-dimensional nested dictionary:

• Dictionary maps indices (1-based) of monomeric forms to
  • Dictionaries which map types of components of monomeric forms ('monomer' or 'backbone') to
  • Dictionaries which map indices (1-based) of atoms to atoms (instances of openbabel.OBAtom)

Example:

{
    1: {
        'monomer': {
            1: openbabel.OBAtom(),
            2: openbabel.OBAtom(),
            ...
         },
        'backbone': {
            1: openbabel.OBAtom(),
            2: openbabel.OBAtom(),
            ...
         },
     },
    2:  {
    ...
    },
....
}