GPG fingerprint improvements

[tyll]

Nogging supports GPG fingprints as key ids. I would like to propose a few improvements:

• Accept only GPG fingerprints instead of key ids (so 40 hexadecimal characters), as discussed in the past in Store and show only GPG fingerprint instead of ID fas#137 for FAS 3. There is no value in storing the key ID instead of the fingerprint and if someone needs to lookup the key id, they can just look up the fingerprint instead.
• Accept the GPG fingerprint with the usual formatting hat is used to display it, for example 18A0 E3D6 A361 94E0 A6F2 C5F0 6A3A 10B3 1C10 9517
• Show the GPG fingerprint with the usual formatting even if the user specified it without the formatting