SusiDNS: Reduce memory usage in AddressBean

by storing destinations in binary instead of base64, to make retrieval from database more efficient. It was written in the hosts.txt days but now that we have binary storage in blockfile, it's better to defer conversion until necessary. This is more important for sort-by-date where we have to pull in all the entries. 1 of 2, additional improvements for sort-by-date to follow in a separate MR or commit.