新增SB Admin2模板

模板功能：

• Fixed, responsive top menu bar with category dropdowns
• Fixed, responsive side menu bar with second level dropdowns
• {"3 custom panel colors"=>"red, yellow, and green"}
• Flot and morris.js jQuery charts
• Basic Bootstrap components included
• Breadcrumb navigation
• Blank page for starting projects
• Widget panels for easy data presentation
• Unstyled format that integrates well with many Bootstrap UI kits