PLT-2257 Reorganized System Console (#3003)

* Reorganized system console

* Fixed the names of some components

* Fixed timestamp for BrandImageSetting

* Fixed merge issues

* Updated push notification settings to match master branch

* Removed top level setting pages and moved enable Gitlab/LDAP settings onto their respective pages

* Re-added restrictDirectMessage setting to system console

* Re-added email connection test and fixed some margins

* Fixed ESLint errors

* Renamed Authentication > Onboarding to Authentication > Email in the system console

* Renamed Customization > Whitelabeling to Customization > Custom Branding in System Console

* Re-added EnableOpenServer to system console

webapp/components/admin_console/settings_group.jsx

@@ -0,0 +1,42 @@
+// Copyright (c) 2015 Mattermost, Inc. All Rights Reserved.
+// See License.txt for license information.
+
+import React from 'react';
+
+export default class SettingsGroup extends React.Component {
+    static get propTypes() {
+        return {
+            show: React.PropTypes.bool.isRequired,
+            header: React.PropTypes.node,
+            children: React.PropTypes.node
+        };
+    }
+
+    static get defaultProps() {
+        return {
+            show: true
+        };
+    }
+
+    render() {
+        if (!this.props.show) {
+            return null;
+        }
+
+        let header = null;
+        if (this.props.header) {
+            header = (
+                <h4>
+                    {this.props.header}
+                </h4>
+            );
+        }
+
+        return (
+            <div className='admin-settings__group'>
+                {header}
+                {this.props.children}
+            </div>
+        );
+    }
+}