Rewrote the batch job processing daemon.

It now shuts down gracefully, completing the current job item. General
daemon handling code is now also better, including PID file handling.



git-svn-id: https://humgenprojects.lumc.nl/svn/mutalyzer/branches/refactor-mutalyzer-branch@238 eb6bd6ab-9ccd-42b9-aceb-e2899b4a52f1