yvSNX v2 Vault <> Curve strategies

[fubuloubu]

Note, this was previously proposed by @mattdw here:

Proposal: Create a ySNX vault to stake on Mintr

Summary: Create a ySNX vault with integration into Mintr and Curve to maximize return on investment and save on gas costs. Abstract: Should this proposal be implemented, a ySNX vault will be created. Users would deposit their SNX to the vault for deployment into both Mintr for the weekly claims and Curve with the generated sUSD. With the proposed strategy, the current APY is roughly 60% for users. Deployment of this vault would act symbiotically to improve the value of yearn, Synthetix,…