Paper under review at Foundations of Physics 
 
PACS 03.50.-z, 03.50.De, 03.50.Kk, 03.65.-w, 03.65.pm, 03.65.Ta, 11.10.-z, 11.15.Kc, 11.30.Pb, 11.09.+t, 12.90.+b, 14.60.Cd, 4.70.Bh