Build error: The type or namespace name 'UnityEditor' could not be found.

The UnityEditor namespace is not available in builds.

The easy solution is to put the script in a folder named Editor. Anything inside of folders named Editor is not included in builds. Since the entire script can be excluded you should do this.

Side note: When you want to exclude only part of a script you can enclose it in compiler flags.

 // Runtime code here
 #if UNITY_EDITOR
     // Editor specific code here
 #endif
 // Runtime code here
 

Side note 2: Your ClearPlayerPrefs class should inherit from ScriptableObject since it shouldn't be attached to objects.

http://answers.unity3d.com/questions/576746/build-error-the-type-or-namespace-name-unityeditor.html