http://www.cnblogs.com/zeejun/archive/2012/08/08/2629064.html
启动界面：Default.png(320x480) Default@2x.png(640x960)
图标:Icon.png(57x57) Icon@2x.png(144x144) Icon-Small-50.png(50x50) Icon-Small.png(29x29) Icon-Small@2x.png(58x58) Icon-72.png(72x72) iTunesArtwork(512x512)