- Add support for requesting an encrypted reply
* NetDB:
  - Add support for encrypted DatabaseSearchReplyMessage and DatabaseStoreMessage
    in response to a DatabaseLookupMessage
* PRNG: Cleanups using Collections.singletonMap()
* Router utils: New RemovableSingletonSet
* TransientSessionKeyManager:
  - Support variable expiration for inbound tag sets
  - Several efficiency improvements
* VersionComparator: Add static method, use most places