catena-Poly[[(1,10-phenanthroline-κ2 N,N′)lead(II)]-di-μ-nitrato-κ3 O,O′:O′′;κ3 O:O′,O′′-[(1,10-phenanthroline-κ2 N,N′)lead(II)]-bis(μ-2,2,2-trichloroacetato-κ2 O:O′)]