[Feature] UI for revoking individual certificates

[rjchow]

A drag and drop UI for revoking individual certs so that they don't need to figure out what the merkle root is

We got a little mixed up on the hash to use for revoking the cert.
We revoked the "proof" of one of the certs, and it revoked another cert from the same batch, and realized it was because it was the "target hash" of that cert.
It would be good to get some clarity on the proof data in the cert.

Originally posted by @yvonneyong in OpenCerts/opencerts-documentation#54 (comment)

[thefiend]

Added in #123 .

[thefiend]

Comments:

• Modal confirmation after drag and drop seems redundant and slows down the flow and serves no purpose, either put in document information for user to check and confirm or remove it - Laurant
• Adding an option to select individual certificate (certificate target hash) or whole batch of certificate (merkle root) to revoke - RJ
• We should add this warning as well when revoking through hash - Laurant

Suggested Flow: