removed empty icon reference
added missing resource files:
  * Icon-60.png      60 x 60    iOS7 iPhone App Icon
  * Icon-60@2x.png  120 x 120   iOS7 iPhone App Icon for retina display
  * Icon-76.png      76 x 76    iOS7 iPad App Icon
  * Icon-76@2x.png  152 x 152   iOS7 iPad App Icon for retina display
Added iOS7 icon file resources to Xcode Project
Merge pull request #299 from Spielmeister/resourcefixes

Added missing icons for iOS7