Updating configuration script to remove double quota warning ( fix #1380 ) + removing some useless comments

Fixing *more* Lintian reported bugs: out-of-date-standards-version, maintainer-script-lacks-debhelper-token, dh-clean-k-is-deprecated, using-question-in-extended-description-in-templates, executable-is-not-world-readable, malformed-question-in-templates

  - now we can it the back button to go back a question. 
  - The questions are a little more clear ( still needs some work )
  - adding a function valid_ip() to check IP addresses before using them.

Probleme quand le FQDN a des majuscules

ADDING fixperms in POSTinst instead of PREinst, FIXING acl mountpoint detection on cryptsetup and ext4 systems

to be able to install an alternc instance on a LXC, I need to fix the quotaon call + skip the acl test...

Gros changement : comme discuté sur la ML, alternc.install n'est plus lancé automatiquement lors de l'installation, l'utilisateur doit le lancer manuellement
pour finir l'installation.

Changements significatifs :
 - l'installation génére et applique les template dovecot et postfix
 - un utilisateur MySQL dédié est maintenant créé pour postfix et dovecot (mail_user).
 - ajout d'un utilisateur systeme pour dovecot pour le mail delivery

starting this release, only named.conf.options will be replaced (as we
need to modify the options {} block and can't just add another one). We
still install a named.conf, a fresh version from Lenny this time, so
that we get a clean start.

Also get rid of the bind_internal parameter that is not really used or
recommended, as it allows for authoritative nameservers to also serve
recursive queries (which is bad practice).

See: #1025
Closes: #1104

postfix

also split the config prompts between slave and non-slave package

See: #1029

note that we discarded some suggestions options:

F_LOG: replaced with syslog
DAEMON: will be considered for inclusion later
VERBOSE/DEBUG: available through command line flags

TYPE_NAME_BACKUP and ALLOW_OVERWRITE_BACKUP are being renamed to
SQLBACKUP_TYPE and SQLBACKUP_OVERWRITE. this is to be more consistent
with the global configurations

See: #1081

also fix database user variable expansion in debian configuration. without this, it is probably not possible to change the database user from the debconf prompts

See: #318.

As of now, the MySQL configuration used everywhere by AlternC is not
stored in the main configuration file (/etc/alternc/local.sh) but in a
MySQL configuration file in /etc/alternc/my.cnf, which enables us to
call mysql without exposing the password on the commandline.

The changes here are quite invasive but will allow us to factor out
the MySQL configuration better. See #364.

This includes a partial rewrite of the mysql.sh logic, which is now ran
from the postinst script (and not alternc.install) which will allow us
to actually change the MySQL root user properly. See #601.

This commit was tested like this:

 * clean install on etch (working)
 * upgrade from a clean 0.9.7 (working)

only reset the welcomeconfirm prompt if it gets refused so it shows up only once, on first install. See #737. This prompt should simply go away at some point, or we could modify it to tell the admin where the backups are.

On passe le path d'install d'alternc en priority low, et on rajoute un warning, il faudrait rajouter de la couleur si c'est possible pour attirer l'oeil et montrer qu'il faut faire attention
Close: #785