Add networked varys

[qaisjp]

To fix now:

• In-memory seems to be a little bit buggy and crashes occasionally, seemingly due to a bug in the memconn library (should we just use a unix socket?)

  If we do end up just using a unix socket, in-memory should automatically create a temporary socket somewhere.

To fix in a future PR:

• Haven't tested reconnections, and haven't written any new logic here. Likely to not work properly. (I think it sends Quit commands to each puppet too...)
• Ok so now I've turned off Quit on varys client disconnect. Now I need to add data sync when connecting, right now it just reconnects. (Maybe I should make connects just a nop instead...?)

[qaisjp]

ten days ago, i cut my small test server over to this branch implementation (using memconn, and not a separate server), and they haven't crashed yet!

[qaisjp]

Okay, running a test now with separated client/server varys