Display confirmation on "Log out everywhere" in the upper right menu

addresses #765

www/common/common-ui-elements.js

@@ -1886,9 +1886,12 @@ define([
                 },
                 content: h('span', Messages.logoutEverywhere),
                 action: function () {
+                    UI.confirm(Messages.settings_logoutEverywhereConfirm, function (yes) {
+                        if (!yes) { return; }
                         Common.getSframeChannel().query('Q_LOGOUT_EVERYWHERE', null, function () {
                             Common.gotoURL(origin + '/');
                         });
+                    });
                 },
             });
             options.push({