Draft: Ratman async overhaul

This milestone consists of a few sub-tasks:

• A new client API encoding, based on frames and discrete command chunks
• A new command line interface for ratctl and map it onto the new client API
• Processing one chunk at a time. Each chunk produces at least one ERIS block worth of data. The chunk size should be chosen based on target chunk size and total message size. For example, a message producing 3 1K blocks doesn't need to be transported in a 8M chunk. Streaming a 10GB movie might warrant the 8M chunks however.
  • Encrypt the chunk with ChaCha20, the shared key derived from a diffie-hellman between the sender and recipient (public key address from recipient, and private key from keystore for the sender).
  • Create a block from the chunk and stream it into the journal
  • Slice the message into a set of carrier frames
  • Dispatch the frames along the most effective endpoint driver/ route
• Investigate spawn strategies and default configurations. Following are a few questions:
  • Can we combine async "bundles" to allow running on truly single threaded (i.e. embedded) platforms?
  • Can we "split" an async environment to run across two cores, while sharing data structures between them?
  • How do we spawn the worker threads for large message transfers? How large does a message have to be for the request to be handled by a dedicated thread? Do we have a thread pool regardless? How do we handle varying sized of available threads to make sure resources are not underserved?
  • Etc... :S
• Port the existing http stack to a tokio-backed framework (warp?)