Resume download and checksum

[luizirber]

Hi,

I tried out the client and got a 502 error a couple of times with the strain_madness dataset. Two suggestions:

1. implement a resume partial download option (like wget -c)
2. add a checksum (sha256? md5?) to the linkfile, so the user can check if the downloaded file is correct.

Thanks!

[alienzj]

@luizirber I fully support your suggestion.