[MMTK] ChemicalObjects.py MMTK 2.5.13

[Guido Wagner]

Hi !

I updated from MMTK 2.5.7 to MMTK 2.5.13 and had problems using the molecule 
factory. The example molecule_factory.py that comes with MMTK does not work 
too. In the new version of ChemicalObjects.py the tests

"""
if blueprint is not None:
	...
"""

are removed. I did not check why they shold be necessary or not, but if I add 
the test again to line 749 (new version) the example and my program work 
fine.

CU Guido Wagner