Update documentation to refer to 2D depictions and avoid confusion the the HydrogenPlacer.

Signed-off-by: Egon Willighagen <egonw@users.sourceforge.net>
Link to the Wiki page in the documentation.

Signed-off-by: Egon Willighagen <egonw@users.sourceforge.net>
Resolve PMD warning - same method/field name.

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