[iOS] enable loading js cache

http://stackoverflow.com/questions/7630291/shouldstartloadwithrequest-not-getting-called-in-subclass

http://stackoverflow.com/questions/4708904/shouldstartloadwithrequest-not-loading-links-when-clicked-on-in-uiwebview

http://stackoverflow.com/questions/9279968/dynamically-loading-javascript-files-in-uiwebview-with-local-cache-not-working