Setting up to use OBDotNet in the acceptance tests

OBDotNet is the compiled assembly for the .NET version of Open Babel
(http://openbabel.org/wiki/Main_Page)

In the acceptance tests I want to parse a SMILES string using OBDotNet and use
that to validate the results from FMol.SmilesParser.

I've just taken the OBDotNet assembly (and its dependencies) from the windows
installation of the OpenBabelGUI. This assembly was compiled for x86 so I've
changed the acceptance tests project to specifically target x86.

I've also added a post-build step to the acceptance project to copy the OBDotNet
dependencies into the output folder. I'm not sure if I've got all the dependencies
(or some that I don't need)...I'll revisit this if it causes an issue.

The acceptance tests will need to be run with an x86 version of NUnit.
Use OBDotNet to verify the FMol parser results in the acceptance tests

Convert the SMILES input with both OBDotNet and FMol then compare them.

Comparing the atoms is simple - just compare the element symbols.

Both parsers store the atoms in the order they appear in the SMILES input so
the bonds can be compared by checking the atom indexes at each end of the bond
and the bond strength.

OBDotNetExtensions contains some helper extension methods for converting OBDotNet
objects for easier comparison with the FMol results.

GetFMolBondType is a bit messy (see the comments in the code), and this is also
the reason for the separate tests for SMILES inputs in aromatic form and Kekule
form. This should be able to be simplified as the FMol parser gets more
functionality for dealing with aromatic rings, etc.