add python interface with optional numpy support for lammps_gather_bonds()

unit tests are included

unittest/python/in.fourmol

@@ -0,0 +1,25 @@
+variable  units           index  real
+variable  input_dir       index  .
+variable  data_file       index ${input_dir}/data.fourmol
+variable  pair_style      index 'zero 8.0'
+variable  bond_style      index zero
+variable  angle_style     index zero
+variable  dihedral_style  index zero
+variable  improper_style  index zero
+
+atom_style       full
+atom_modify      map array
+neigh_modify     delay 2 every 2 check no
+units            ${units}
+timestep         0.1
+
+pair_style       ${pair_style}
+bond_style       ${bond_style}
+angle_style      ${angle_style}
+dihedral_style   ${dihedral_style}
+improper_style   ${improper_style}
+
+read_data        ${data_file}
+dihedral_coeff   *
+improper_coeff   *
+