The Caching Module Caches the images that have been extracted and for
persistence writes the images to a cache file.
In the cache file the data is stored by tab separated values
`%s\t%s\t%s`
the cache is first loaded in the memory ( CACHE_LIST ) during the start of application
and then extracted images are added to the map CACHE_LIST which is
writtern to the cache file before exiting the program.