Auto-detect when a terminal is connected

[AESilky]

If the device is booted without a terminal connected and then a terminal is connected, the terminal display is garbled (due to it missing VT220/ANSI configuration that is sent during start up). The interface provides a '^R' hotkey to refresh the screen (which sends the terminal configuration again). This results in the display being correct.

It would be nice if MuKOB could detect when a terminal is connected (and not) so the display would auto correct without needing the '^R'. Also, if MuKOB knows that there isn't a terminal, it could avoid wasting time sending information to it (there are constant updates occurring for the time, the state of the key, Wi-Fi, etc. that take time to send to the terminal over the serial connection).

It would be acceptable if it took a brief period to recognize that a terminal is connected/disconnected (2-3 seconds would probably be okay), if the '^R' hotkey was still supported for an immediate update if desired.