[iPhone] Based on iCloud, need to change the data storage directory

iOS data storage guideline :
https://developer.apple.com/icloud/documentation/data-storage/

Problem :
Since iCloud will sync the data in 'Documents' directory, we need to change the data storage directory to 'Librarys/Caches/ if it's not users related data.

Solution :
Replace 'NSDocumentDirectory' by 'NSCachesDirectory' while saving data.