Implemented encoding of Multiple Request Service command
o Added test_logix_multiple unit test
Working parser for Multiple Request Service request
Full round-trip of Multiple Service Packet request/reply
o Correct naming
o Propery parse raw request data payload into .multiple.request_data
o Reply parser not yet complete
Implement full parsing of Multiple Service Packet request/reply
o Create cpppo.dfa_post to allow scheduling of post-processing
  closures from within a running DFA.
o Use cpppo.dfa_post to implement parsing of Multiple Service
  Packet sub-requests possibly using the same DFA already in use.
Fully operational Multiple Service Packet request/response
o Add cpppo.server.enip.client --multiple option
o For Message_Router.parser to parse a Multiple Service Packet response,
  we must simply default to use the Message_Router's parser; we do not
  have the original request's path which may have specified a different
  class ID or instance ID.  By default, we use a Logix Message_Router
  in the cpppo.server.enip.client.
Add cpppo.server.enip.client --multiple docs, roll __version__ to 2.8.0
Merge branch 'feature-multiple-request'; Version 2.8.0