Allow for Gnosis Safe to be used for veBAL locking

This proposal is to allow for Gnosis Safe smart contracts to be used for locking veBAL and staking liquidity in the new Balancer rewards scheme.

It is obviously beneficial to have one of the most popular multi-sig tools to allow for locking. Most DAOs use Gnosis Safe. It it not something that should be prevented.

We cannot allow all Gnosis Safes to lock. You need to request your specific safe is whitelisted for locking veBAL. In order for us to approve it, we need information about why you need to lock through a safe, who you are, etc.