Include hash value of zip files

[FritzHeiden]

As discussed in cta-wave/dpctf-deploy#78 the database.json should include the hash value for each referenced zip file. This allows to check for updates in the content and avoid unnecessary re-downloading.

[rbouqueau]

Need seems standard and I support it. In practice updates won't happen because of the aggressive caching on the Akamai server - we just don't overwrite.

[FritzHeiden]

This can be closed without further action when this gets approved: cta-wave/dpctf-deploy#78 (comment)