Fix Update errors

I closed my last merge-request, as the request included all the upstream commits. I recreated my fork to get a clean environment.

Changes i've done are listed in commit f9d95c0c

* i don't have mailman installed, but update.php tried to configure it
* i also fixed the check for doveadm in suse & fedora lib, but it seems my centos dovecot does not have "doveadm mount" subcommand, so i think the doveadm error will still exist
* on centos the 'receive_override_options = no_address_mappings' was added to postfix main.cf which leads to not working e-mail aliases/forwards

Reconfigure Services? (yes,no) [yes]: /ispconfig/ispconfig3/tree/master/

Configuring Postfix postalias: fatal: open /var/lib/mailman/data/aliases: No such file or directory Configuring Mailman
PHP Warning: chgrp(): Unable to find gid for mailman in /usr/src/ispconfig3_install/install/dist/lib/fedora.lib.php on line 106 Configuring Jailkit
Configuring Dovecot
usage: doveadm [-Dv] [-f ] []

altmove [-u |-A] [-S ]
auth [-a ] [-x ] []
config [doveconf parameters]
director add|flush|map|remove|status
dump [-t ]
expunge [-u |-A] [-S ]
fetch [-u |-A] [-S ]
force-resync [-u |-A] [-S ]
help
import [-u |-A] [-S ]
kick [-a ] [-f] [|]
log find|reopen|test
mailbox create|delete|list|mutf7|rename|status|subscribe|unsubscribe
penalty [-a ] []
purge [-u |-A] [-S ]
pw [-l] [-p plaintext] [-r rounds] [-s scheme] [-u user] [-V]
reload
search [-u |-A] [-S ]
sis deduplicate|find
stop
user [-a ] [-x ] [...]
who [-a ] [-1] [] []
Configuring Spamassassin
Configuring Getmail
Configuring Database

- Make sure full cron jobs are written unchanged; with the previous version, a cron job like "cd /var/www/example.com/web/ && /opt/php-5.4.23/bin/php shopware.php /backend/cron" was changed to "/var/www/clients/client1/web1/cd /var/www/example.com/web/ && /opt/php-5.4.23/bin/php shopware.php /backend/cron" which of course does not work.

- simply call nginx -t instead of /usr/sbin/nginx -t; works if nginx is not located in /usr/sbin, but elsewhere in the PATH.

- nginx: do a syntax check because on some distributions, the init script always returns 0 - even if the syntax is not ok (how stupid is that?)

Changed web folder permissions in nginx setups from 711 to 751 to avoid (false) permissions warnings in log files.

Fixed: FS#3456 - Dashboard Style still broken after Update to 3.0.5 // Patch 3053_dashboard does not work

Fixed: FS#3440 - after each install/reconfigure: warning: database /var/lib/mailman/data/virtual-mailman.db is older

- Added missing option in centos dovecot.conf file