Filter by commodity

Added a commodity dropdown selector on our Data Search page. The filter lets you conveniently filter out all curves for power, gas, and other commodities. Combining the commodity picker with a country, say "German power", returns all supply and demand-side factors, historical data, multiple forecasts, derived data like fundamental climate, seasonal normal, capacities, etc., for Germany. Note that data resolution and definition are also reconciled. Timesaving and convenient.