allow —-kill-waittime parameter to specify the kill timeout

[lacco]

As already described in #459 , the default kill timeout of 20 seconds of the daemons gem might be not appropriate for every project, especially when having long running jobs. Currently, it is not possible to pass a different timeout, even #916 doesn't help here because the force_kill_waittime is a Ruby option.

Based on the work of @pacoguzman in #459 , I added an additional command parameter --kill-waittime=n.