Merge branch 'stable-3.1' into 'stable-3.1'

install/dist/lib/fedora.lib.php

install/lib/install.lib.php

install/sql/incremental/upd_dev_collection.sql

install/sql/ispconfig3.sql

install/tpl/apache_apps.vhost.master

install/tpl/server.ini.master

interface/lib/classes/system.inc.php

interface/lib/classes/tform_base.inc.php

interface/web/admin/form/server_config.tform.php

interface/web/admin/lib/lang/ar_server_config.lng

interface/web/admin/lib/lang/bg_server_config.lng

interface/web/admin/lib/lang/br_server_config.lng

interface/web/admin/lib/lang/ca_server_config.lng

interface/web/admin/lib/lang/cz_server_config.lng

interface/web/admin/lib/lang/de_server_config.lng

interface/web/admin/lib/lang/dk_server_config.lng

interface/web/admin/lib/lang/el_server_config.lng

interface/web/admin/lib/lang/en_server_config.lng

interface/web/admin/lib/lang/es_server_config.lng

interface/web/admin/lib/lang/fi_server_config.lng