Add a version check to kegboard_daemon.
Add a version check to kegboard_daemon.

This will allow for future, backwards-incompatible firmware changes.

A side effect of this change is that all but those kegboards flashed with the
most recent firmware version (v4) will be treated as incompatible. This is
intentional, since recent changes to onewire device handling require an update.

Kegbot/kegbot-server,Kegbot/kegbot-server,Kegbot/kegbot-server,Kegbot/kegbot-server,Kegbot/kegbot-server