Added support for specifying feature CSS files in menu.xml

Eg:
        <item>
            <hash>mon_infra_dashboard</hash>
            <label>Dashboard</label>
            <rootDir>/monitor/infra/dashboard/ui</rootDir>
            <view>monitor_infra_dashboard.view</view>
            <js>monitor_infra_dashboard.js</js>
            <css>test.css</css>
            .....
        </item>