MDL valence model.

Signed-off-by: Egon Willighagen <egonw@users.sourceforge.net>
Use the MDL valence model when reading molecules with the V2000 reader.

Signed-off-by: Egon Willighagen <egonw@users.sourceforge.net>
Write valence if it does not match the MDL implied valence. The option to 'writeQeuryFormatValencies' has been removed - the valence field is a generic field and can always be written.

Signed-off-by: Egon Willighagen <egonw@users.sourceforge.net>
Correct handling of aromatic type - fixed typo and also check bond order is set to 'UNSET' not null.

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