Issue #839444 by mkalkbrenner, andypost, gnunes, hchonov, voleger,...

Issue #839444 by mkalkbrenner, andypost, gnunes, hchonov, voleger, claudiu.cristea, keichee, gease, kfritsche, wells, sokru, tstoeckler, quietone, ravi.shankar, Damien Tournoud, Berdir, Fabianx, catch, Wim Leers, larowlan, kristiaanvandeneynde, twistor, daffie, alexpott, sun: Make serializer customizable for Cache\DatabaseBackend