--non-stop mode error handling

[jesseangell]

--non-stop is not that tolerant of db servers dropping connections or other random issues that could occur when something is running for extended periods of time. mogbak itself is very good about resuming a backup that it crashed on but if --non-stop crashes it's not going to automatically start.

Need to get better about rescuing database exceptions and handling them in a sane manner -- perhaps pause and retry later if it can't connect..etc