change pass phrase of any key

[tomholub]

Currently, changing pass phrase only changes it for the first key in storage (treated originally as "primary key", but going forward we want to treat all keys the same).

If current pass phrase is not known, the user is asked for the pass phrase to change, after which they can change it.

Currently, pass phrase (of only the first key) can be changed in security -> change pass phrase.

Instead we could add functionality to change pass phrases to here:

Then we can do it on a per-key basis. Just update (remove) with (remove, change pass phrase). Then we need to pass the fingerprint of the key we are modifying into the change_passphrase screen.