Polymer Pendant Ligand Chemistry-5. The Selective and Competitive Removal of Ag+, Hg2+, Cu2+, Pb2+ and Cd2+ Ions from Aqueous Solution Utilizing a N-Sulfonylethylenebis(Dithiocarbamate) Ligand Anchored on Macroporous Polystyrene-Divinylbenzene Beads