NSObject(NSValue) Fix

The `NSValue` category of `NSObject` overwrites any property named `value` of any object.
It was overwriting my `NSManagedObject` property so I think it might not be too good to keep with this name, so I prefixed it with the project name, so it's now named `NSObject(NSValue)#fe_value`.

Also removed a duplicate file with different case that was generating a conflict since my OSX is set to case insensitive.