Main:All Added per CMS config for sub-modules

If CMS is installed and a sub-module requires to be configured per CMS,
this is handeled by new 'CMSHook-(pre)conf.sh'
this has been added to Dev Docs

Updated postfix sub-module to use new CMSHook
Added 'itype' var for detection of install script type
Now also storeing  'Allways on modules' in installer as EnabledAons

SubModules/postfix/preconf.sh

@@ -1,7 +1,3 @@
-if [ -z "${domain}" ]; then
-    postfixappended=1
-fi
-
 if [ "$shortdist" = "ubu1804" ] || [ "$shortdist" = "ubu2004" ] || [ "$shortdist" = "deb10" ] ; then
     debconf-set-selections <<< "postfix postfix/mailname string $hostname"
     debconf-set-selections <<< "postfix postfix/main_mailer_type string 'Internet Site'"