BZ 425612 - Move base64 to Jackson and outside getters/setters

Signed-off-by: Paulo Lopes <pmlopes@gmail.com>

base64 encoding happens on set and on get. Although this would be ok, for JsonArrays since there is no getBinary this breaks the API where one can put a byte[] into the json but never do the reverse. If the encoding/decoding happen and serialization/deserialization it solves this issue and one does not need to do extra checks or multiple encode/decodes if the getter/setter is called multiple times.