Prop 147: Token Registry Proposal: Adding DYDX.

This is a token registry proposal to adding DYDX. Please vote 'Yes' if you support to this proposal, and 'No' if you oppose it. Commonwealth post for DYDX: https://commonwealth.im/ux/discussion/14074-list-dydx?tab=0. Please update your price feeder config to support DYDX.