Sysadmin reconstruct settings (#3946)

* sysadmin reconstruct settings page

* [system admin] settings: refactored it

* fixup & improvement

frontend/src/pages/sys-admin/side-panel.js

@@ -65,10 +65,14 @@ class SidePanel extends React.Component {
                 }
                 {constanceEnabled && canConfigSystem &&
                   <li className="nav-item">
-                    <a className='nav-link ellipsis' href={siteRoot + 'sys/settings/'}>
+                    <Link 
+                      className={`nav-link ellipsis ${this.getActiveClass('web-settings')}`}
+                      to={siteRoot + 'sys/web-settings/'}
+                      onClick={() => this.props.tabItemClick('web-settings')}
+                    >
                       <span className="sf2-icon-cog2" aria-hidden="true"></span>
                       <span className="nav-text">{gettext('Settings')}</span>
-                    </a>
+                    </Link>
                   </li>
                 }
                 {canManageLibrary &&