Automatic renewal of cached files downloaded by FileCacheDataLoader

Created by: rvillido

This modification adds automatic renewal functionality of cached files that are downloaded with FileCacheDataLoader. It adds a parameter called 'cacheExpirationTime' that can be used for setting cache expiration time in milliseconds.

We are using it for fetching TSL so that FileCacheDataLoader would cache TSL and not download it every time. The problem is that once FileCacheDataLoader has cached a URL, it will always use it and never renews it.