Pass the Stereocenters instance to the element creation allowing it make a decision about questionable hatch/down bonds.

Signed-off-by: Egon Willighagen <egonw@users.sourceforge.net>
Implementing a procedure to interpret the inverse style down (hatch) bonds when it is unambiguous. This follows IUPAC guidelines on structure depiction that the stereo-center may be at the fat-end of a hatch bond if the configuration is unambiguous.

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