FS#3526 - Add option to disable BIND zone check (the intention for the feature request was more to hide log-messages and not to disable the named-checkzone-call)

Added prefetching to dovecot to halve database-queries
Added mdbox-creation for new Mailboxes in mdbox-format

Conflicts:
	install/tpl/debian6_dovecot-sql.conf.master
	install/tpl/debian_dovecot-sql.conf.master
	install/tpl/debian_postfix.conf.master
	install/tpl/fedora_dovecot-sql.conf.master
	install/tpl/fedora_postfix.conf.master
	install/tpl/gentoo_postfix.conf.master
	install/tpl/opensuse_dovecot-sql.conf.master
	install/tpl/opensuse_postfix.conf.master
	interface/web/admin/templates/server_config_mail_edit.htm
	server/cron_daily.php
	server/plugins-available/mail_plugin.inc.php
	server/plugins-available/postfix_server_plugin.inc.php

-Added a new option "Network Filesystem" under System > Server config > Web to toggle on / off the _netdev option for the bind mounts in /etc/fstab

Use dovecot or maildrop in default-cases
Switching to LMTP and back included in server-postfix-plugin
validator added to disable switching uid-mapping when already created mailusers or in multiserver-environment

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Feature can be activated over admin mailserver settings. when activated websites uid is used instead of standard vmail-uid. this only takes effect if web and mailserver are on the same server, otherwise it will be old behaviour. switching this setting when mailboxes exist doesn't matter. Mailboxfolder will be created with website uid for this. access of postfix and dovecot now works over mysql-table mail_user. virtual_uid_maps is changed from static to mysql-table. for dovecot<->postfix communication protocoll is changed vrom lda to lmtp. disablelmtp-column is added to mail_user-table. uid and gid can be overwritten by remoting.
ONE OPEN ISSUE: since remoting has completly changed and mail_user_add function is missing at the moment, this function now was inclulded again. it is important to add the both new lines to the future function and then remove this new one.

Reverted SVN trunk back to revision 3938 to remove changes in default theme an a replacement of the ispconfig logo.

- Added backup size to web backups