Determination of Degree of Ionization of Poly(Allylamine Hydrochloride) (Pah) and Poly[1-[4-(3-Carboxy-4 Hydroxyphenylazo)Benzene Sulfonamido]-1,2-Ethanediyl, Sodium Salt] (Pazo) in Layer-By-Layer Films Using Vacuum Photoabsorption Spectroscopy