global option to enable pagespeed with nginx - allows to enable pagespeed even if no webserver-config is selected

Added a server migration mode setting which will be used to prevent that LE tries to recreate certs during a server migration.

Known Bugs: CMK-URL is damaged (origtarget), iframe stays white...?

Known Bugs: CMK-URL is damaged (origtarget), iframe stays white...?

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

see:
- http://git.ispconfig.org/panders/ispconfig3/commit/f7ec00b2f8ba3efc5bdeacef9c813f8a826ae3be#note_448

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

- Added HHVM to "Default PHP Handler" field (server configuration).
- Fixed "Unable to load the server configuration from database." error when running server.sh.
- Fixed Javascript (accordions weren't working anymore, directive snippets and other placeholders couldn't be added anymore).

-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