图标（Icon）大小详细说明：
https://developer.apple.com/library/ios/documentation/UserExperience/Conceptual/MobileHIG/IconMatrix.html
开发指南：
https://developer.apple.com/library/ios/navigation/#section=Resource%20Types&topic=Guides
iOS开源工具下载
https://developer.apple.com/downloads/
属性列表字段
https://developer.apple.com/library/ios/documentation/General/Reference/InfoPlistKeyReference/Articles/AboutInformationPropertyListFiles.html