Comparing hashes of data to prevent saving the same data (2): compare hashes + either store or point to previous version

[mjia8]

Team members: Jayesh, Kajoyrie, Jason
Sprint 5: 6/26-7/3

Overall Goal:
After creating a hash, we see if it is different from the hash of the last version of the data. If it is different then we store the hash of the new data and the timestamp. If it is not different to the previous hash, we do not store the hash the second time and instead we want to have entry in the registry telling us that we downloaded the second time and it was the same hash as the previous version. This can be done as an additional attribute or have the path point to the previous file with the previous timestamp.