Add daemonize bundle

Ref: https://dev.cfengine.com/issues/6307

See this conversation on help-cfengine:

https://groups.google.com/forum/#!topic/help-cfengine/P1yHW7OWirQ
I would use this, absent other options (daemonization tools that do more than just disconnect pipes to prevent zombies, or a proper `daemon => "true"` option for commands).  I'd also love to see a usage example and a note on platform compatibility (which Unices and which shells).

Quoting may be especially tricky and should at least be noted as a gotcha.  Recently on help-cfengine we were talking about the complicated rules for single and double quotes.