Add support for looking up supervisord::program through hiera

[jasperla]

I've explicitly documented the autostart and autorestart parameters in the Hiera snippet as it may cause some confusion as to what their type really is (and how they're validated).

[ajcrowe]

This is a really nice addition, might be good to cover all the resource types? fcgi-program, eventlistener and groups as well to be complete.

[jasperla]

Here you go :)