add swig exception for pdbqt_parse_error

[shazj99]

While doing large scale virtual screening using vina, the python process may corrupt due to invalid atoms in some of ligand pdbqt files. The error shows as bellow:

PDBQT parsing error: Atom type B is not a valid AutoDock type (atom types are case-sensitive).
 > ATOM      1  B   UNL     1       0.126  -0.559   0.434  1.00  0.00     0.400 B

The reason of corruption is the calling of exit() in underlying C++ codes like parse_ligand_pdbqt_from_file() or parse_ligand_pdbqt_from_string(). So we add a swig exception to throw it out instead of exit directly.

The test code is attached here: parse_test.tar.gz

[diogomart]

Thank you @shazj99 for this.