Merge branch 'develop' of git.ispconfig.org:ispconfig/ispconfig3 into develop

install/dist/lib/fedora.lib.php

install/dist/lib/gentoo.lib.php

install/dist/lib/opensuse.lib.php

install/lib/installer_base.lib.php

install/sql/incremental/upd_dev_collection.sql

install/sql/ispconfig3.sql

install/tpl/apache_ispconfig.conf.master

install/tpl/debian_postfix.conf.master

install/tpl/fedora_postfix.conf.master

install/tpl/gentoo_postfix.conf.master

install/tpl/jk_init.ini.master

install/tpl/mysql-virtual_email2email.cf.master

install/tpl/opensuse_postfix.conf.master

server/conf/nginx_vhost.conf.master

server/lib/classes/cron.d/600-jailkit_maintenance.inc.php

server/lib/classes/system.inc.php

server/plugins-available/apache2_plugin.inc.php

server/plugins-available/nginx_plugin.inc.php

server/plugins-available/openvz_plugin.inc.php