fix(daemon leaks): rework main loop and fork() approach

[matteotenca]

fix(daemon leaks): rework main loop and fork() approach

Make the daemon fork() twice, remove the thread and use signals to clean-exit.

Why fork() twice: http://www.faqs.org/faqs/unix-faq/programmer/faq/ at 1.7. Redirect STD* to /dev/null in daemon mode.

Added the -d switch to avoid forking and printing messages to STDERR.

Let me know what you think @pkoutoupis !

Next step is to output JSON without invoking rapiddisk.

Regards

[pkoutoupis]

Since both this and the other PRs are fairly large, I would like to schedule a Zoom call (if you do not mind) to step through them. Can you please reach out at petros AT petroskoutoupis DOT com?

[matteotenca]

Since both this and the other PRs are fairly large, I would like to schedule a Zoom call (if you do not mind) to step through them. Can you please reach out at petros AT petroskoutoupis DOT com?

I'll write you ASAP!

Regards

[matteotenca]

This PR is superseeded by #139, can be closed.

Regards

[pkoutoupis]

Per the request.