Refactored interactions with pond.Message from cli.go and gui.go into
network.go by creating a sendDraft func that calls the ratchet.

I believe this should simplify sending messages to multiple recipiants,
and reduce the chances of making mistakes when writing future UIs.

This should also fix a minor hickup in the GUI where, if the user begins
a reply, but deletes the inbox message before replying, then the reply
loses its status as a reply.