Grant Advisory Board Emergency Powers

Granting Advisory Board specific powers to upgrade smart contracts in emergency situations (3 of 5 required to pass).

During the bug disclosures we realised that the Emergency Pause functionality is useful but a very blunt tool with significant downsides to members. It would be beneficial to have the power to upgrade contracts to fix issues in a less severe way.

At the smart contract level the Advisory Board technically has this power already, as it can change the voting settings on upgrades to itself and then pass an upgrade. So this would be changing the legal documents of the mutual to grant this power.