Merge branch 'stable-3.1'

install/lib/installer_base.lib.php

install/tpl/apache_apps.vhost.master

install/tpl/apache_ispconfig.vhost.master

install/tpl/nginx_apps.vhost.master

install/tpl/nginx_ispconfig.vhost.master

interface/lib/app.inc.php

interface/lib/classes/aps_guicontroller.inc.php

interface/lib/classes/auth.inc.php

interface/lib/classes/remote.d/sites.inc.php

interface/lib/classes/remoting_lib.inc.php

interface/lib/classes/tform_base.inc.php

interface/lib/classes/tools_sites.inc.php

interface/lib/plugins/sites_web_vhost_domain_plugin.inc.php

interface/web/admin/system_config_edit.php

interface/web/client/client_edit.php

interface/web/client/form/client_template.tform.php

interface/web/client/lib/lang/de_client_message_template.lng

...e/web/client/lib/lang/de_client_message_template_list.lng

interface/web/client/lib/lang/en_client.lng

interface/web/client/lib/lang/en_reseller.lng