In order to make it posible to update some parameters of a proof without having to sign the stakes again, we need to reduce the scope of what is signed by the stake. This means that we need to compensate this lack of stake signature score, and this diff creates a new proof signature to achieve that. The proof signs the limited proofid with the key corresponding to the master key, so that no one but the master key owner can update the proof without having the stake to sign again.
Ref T1676.
Depends on D10109.