Project Settings UI uses SHA256 fingerprints instead of MD5

The CircleCI Project Settings UI now displays the SHA256 fingerprints of SSH keys instead of MD5 fingerprints. Users can now specify a SHA256 fingerprint in addition to MD5 in their CircleCI config when adding additional SSH keys to their build.

Note: The CircleCI APIs for managing deploy, user, and additional SSH keys have been updated to accept SHA256 fingerprints. All changes are backwards-compatible.