Changes to image cache to clear the cache on reload of app based on items only staying in the cache for 4 days.

addition of images to an SD card cache, (the cache was there, but nothing ever got added to it)
and removal from that hardware cache.
Slight hack, passing the fileCache through to the inmemory cache get so we can delete from the file cache if we delete from the in memory cache.
Merge pull request #102 from BlythMeister/ImageCache

Changes to image cache