collectdmon: Added a small daemon monitoring collectd.

collectdmon: Added a small daemon monitoring collectd.

This is a small "wrapper" daemon which starts and monitors the collectd
daemon. If collectd terminates it will automatically be restarted, unless
collectdmon was told to shut it down.

Current features:

 * restarting the daemon
 * logging to syslog
 * detection of quickly, repeatedly respawning processes
   (similar to SysV init)

collectdmon is similar to mysqld_safe.

Signed-off-by: Sebastian Harl <sh@tokkee.org>
Signed-off-by: Florian Forster <octo@huhu.verplant.org>