App Ops - Permission Settings APP
Be very careful using this feature. Google purposely made this a hidden feature as there's currently no warning if you break a feature in an app.
Note: this app only works in Android 4.3 up to 4.4.1 and DOES NOT work on Android 4.4.2 onwards (eg Kit Kat or Lollipop).
Source code available at: https://github.com/thewirelessguy/App-Ops