UMIP 104 -Add DFX as a supported collateral type

DFX is a decentralized exchange protocol with a dynamically tuned bonding curve optimized for fiat-backed stablecoins like USDC, CADC, EURS, and XSGD.

The DFX token is the governance token of the DFX exchange. This UMIP will add DFX to the supported collateral currencies on the global whitelist contract, allowing the usage of the DFX token as collateral currency. This serves as an important step to allow for the creation of KPI options for DFX.