MMFF resource files

Signed-off-by: Egon Willighagen <egonw@users.sourceforge.net>
MMFF aromatic types are assigned by updating the existing symbolic types.

Signed-off-by: Egon Willighagen <egonw@users.sourceforge.net>
MMFF atom type assignment, unit and validation tests. The atom types are assign using simple SMARTS patterns and the previously implemented aromatic mapping. This provides correct assignment of all symbolic types in the validation suite.

Signed-off-by: Egon Willighagen <egonw@users.sourceforge.net>
Circumvent '*' not matching explicit hydrogens.

Signed-off-by: Egon Willighagen <egonw@users.sourceforge.net>