Completed parsing of incoming Logix Read/Write Tag [Fragmented]
o Added simple indexing to dotdict keys, and collapse dotdicts containing
  lists of dotdicts, emitting keys containing indexes.
o Correct dotdict.__getattr__ to issue AttributeError instead of __getindex__
  KeyError, so hasattr will work.
o Correct unconnected_send to properly limit the length of the encapsulated
  command payload for parsing, and allow zero-length Port Segment route