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

DKIM: changed config-file-check to prevent saving the keys in the wrong file if a single amavis-config-file exists after upgrading to a "split-config"

- upd: better error handling and logging

Fix for mailrestore, to avoid confusion about web- and mail-backups with same ids

Falko Timme authored Jan 09, 2015 and Patrick Anders committed Jan 09, 2015

- Made sure SQL backups from servers that differ from the server where the website is on can be restored. A download of the backup is not possible in such a case, therefore I hide the "Download" button.

Conflicts:
	interface/lib/classes/plugin_backuplist.inc.php

- Made sure SQL backups from servers that differ from the server where the website is on can be restored. A download of the backup is not possible in such a case, therefore I hide the "Download" button.

see:
- http://git.ispconfig.org/panders/ispconfig3/commit/f7ec00b2f8ba3efc5bdeacef9c813f8a826ae3be#note_455

- http://en.wikipedia.org/wiki/SPDY