CO2 Scenario Overview draft.
Included dummy pie chart.
Refactored CO2.sector_demands structure to fit directly into the graphs.
Refactored CO2 charting functions names and rea-arranged their positioning.
First draft for the Demand pie chart.
Beautified Demand pie chart.
First draft for the Electricity production graph.
Code grooming.
Beautified charts.
Closes #189.
Merge branch 'co2'
Fixed bug with Electricity and CHP emission calculations.