Merge branch 'stable-3.1'

docs/autoinstall_samples/autoinstall.conf_sample.php

docs/autoinstall_samples/autoinstall.ini.sample

install/dist/lib/gentoo.lib.php

install/install.php

install/lib/installer_base.lib.php

install/tpl/mysql-virtual_outgoing_bcc.cf

install/tpl/mysql-virtual_outgoing_bcc.cf.master

install/update.php

interface/lib/classes/plugin_directive_snippets.inc.php

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

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

interface/web/client/templates/message_template_list.htm

...dashboard/lib/lang/bg_dashlet_invoice_client_settings.lng

...dashboard/lib/lang/br_dashlet_invoice_client_settings.lng

...dashboard/lib/lang/cz_dashlet_invoice_client_settings.lng

...dashboard/lib/lang/el_dashlet_invoice_client_settings.lng

...dashboard/lib/lang/en_dashlet_invoice_client_settings.lng

...dashboard/lib/lang/es_dashlet_invoice_client_settings.lng

...dashboard/lib/lang/fi_dashlet_invoice_client_settings.lng

...dashboard/lib/lang/hu_dashlet_invoice_client_settings.lng