* -ZIdentityStorage abstraction -- not ready for prime time.
* -ZSwitch -- was dependent on identity_storage.
* -identity_frame_handlers which have been storing()/polling() socket identities -- same reason, ZIdentityStorage not ready for prime time.
* -PING as abstraction -- was dependent on ZIdentityStorage which in turn was too raw.
* -PingStrategy in the ZWorker -- the same as above.
* updated unit tests.
* +some missed java docs.