added new services, reordered a bit
Updated file name: more generic.

Also, activated a lot of postfix features. All of them aren't working
well currently due to some version problems[1].

We're wanting to use spamassassin as a "pre-filter". Mail flow will be
as follow:
- get caught in Postfix, validated at this level
- sent to spampd service in order to get a score
- sent to gpg-mailgate (to be added) in order to encrypt it
- sent to dovecot in order to push it in the right directory according
  to sieve filters (those will be available only for meta/headers of
  course)

[1] apparently, libnet-dns-perl version shipped with Jessie isn't the
stable version, and a check in some SA plugin fails due to the
non-numeric format version. A bug has been filled at Debian level.
https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=769645