Generate Crc32c and Md5Hash when seeding from disk

[fsouza]

When loading objects from disk, we should also calculate the proper crc32 check and the md5 hash.

[antonydenyer]

This is a broader topic than just calculating hashes.

Currently when using a preloaded data from disk data is fetched at execution time. ie when you call the ListBuckets endpoint the function will read from disk at the point in time. Subsequent calls to ListBuckets will just read from disk again. You could have the scenario where folders/buckets are created without going through the createBucket endpoint. I don't think this is a problem.