Added chroot option to master.cf (supported on Debian), added postgrey c...

...onfig file

Most significantly, this change introduces the parameter
   `postfix_master_services_chroot`
which modifies the column 'chroot (default yes)' in the master.cf file, to turn on chroot for those services that have it enabled by default in Debian.

This change also adds the file:
   /etc/default/postgrey
or
  /etc/sysconfig/postgrey
And brings this under puppet control, so that it is consistent with the postfix setting.
It also allows the user to specify
  `postgrey => 'inet:127.0.0.1:10023',`
instead of simply true/false, so that the parameter `postgrey_policy_service` could be eliminated.
The default setting was changed to `inet:127.0.0.1:10023` because Debian systems do not come with the directory /var/spool/postfix/postgrey/

Lastly, the parameter `maildrop_service` is introduced to allow the maildrop service to be uncommented in the master.cf file.