Rewrite mol2 file format using STL iostreams

[kylelutz]

The mol2 file format should be rewritten using std::istream instead of QIODevice.

The read() method in the Mol2FileFormat class in the sybyl plugin should be changed from:

bool read(QIODevice *iodev, chemkit::MoleculeFile *file)

to:

bool read(std::istream &input, chemkit::MoleculeFile *file)

And the write() method should be changed from:

bool write(const chemkit::MoleculeFile *file, QIODevice *iodev)

to:

bool write(const chemkit::MoleculeFile *file, std::ostream &output)

[kylelutz]

Completed in: ca39e6c2b6f0ce8b529c0cdf59149f3d18b4cd6c