Lots of changes

Switch project to Python 3 (this is an application - why did I bother
with 2?!), add a 3-compatible variant of ipaddr (grrr...), add a base
class for terminal apps (based on bits of oxitopped and picroscopy),
remove termsize (not needed with argparse), and add multi-capture,
video-port-capture, and sync-delay to the server