Add handshake timeout

[gdamore]

With the recent integration of #96 / #102 -- we no longer hang the whole application while waiting for a handshake. But, handshaking of TCP, TLS+TCP, and IPC should complete in a timely fashion, and we should add a timeout that closes connections from peers that do not complete the handshake within a modest period of time.

We propose to set this to 5 seconds by default. Satellite connections can have very long (500ms or so) latencies, but 5 seconds should be sufficient for everywhere in local Earth orbit. Latency to the moon is about 1.3 sec.

One thing we could do to make this a little more forgiving is require forward progress, so that the handshake doesn't timeout in 5 absolute seconds, but times out if no progress is seen for 5 seconds.

This issue does not intend to address timeouts on established connections. That's an orthogonal issue and should be treated separately.

[gdamore]

5 seconds is probably not sufficient for all use cases. Satellite latencies can approach 2 seconds. This is fairly abysmal, but we'll want to set the default a bit higher. NNG chose 10 seconds.