Consider templatizing outgoing data buffer container

[cliffg-softwarelibre]

As of April 2019 outgoing buffers are hard-coded to const-shared-buffer. This could be templatized, allowing application code to use other types for outgoing buffers. However, the hard constraint on the type is that the lifetime of the underlying data buffer must be valid until notification is received within chops-net-ip that the data has been delivered. const-shared-buffer is a reference counted buffer, which satisfies this constraint. Buffers that move may also satisfy this constraint, although some analysis needs to be performed. Static / global data buffers also satisfy the constraint, although then it is up to the application to manage which static / global buffer is being used or not.

Making this design change will affect many portions of the code and API, so this is not a simple or trivial redesign.

[cliffg-softwarelibre]

Note that this is not critical for first release (it is not listed as first release criteria), but will definitely be mentioned in "under consideration for future release".

This also is related to issue #35 and #10. I'll add a discussion item (for Nathan and Roxanne) in the team discussion area.