Bitcloud.JS: pack and unpack message as JSON with binary attachment and save message output to file system

[gnostication]

• Pack some binary attachment with JSON and write full message to file system.
  ** Inspect the output
  ** Ensure the JSON is correct
  ** Hash the message and validate message is error free
• Open, unpack the entire message, and output the binary attachment as a file.
  ** Check output file to verify that it still works.