Graphical gas price selection (#2898)

* Added gasPriceStatistics

* WIP graph fas price stats (#2142)

* Chart to select gas price in Extra Tx (#2142)

* Gas Selection UI

* Gas Price Selection: better UI (right octiles, point on graph) (#2142)

* Gas Price Selection chart update using D3 (#2142)

* Working UI, more fluid... (#2142)

* Using the new gasPriceHistogram Call: display histogram (#2142)

* Code Clean

* Updated gas Selection explaination

* PR grumble // Gas Price Selector (#2898)

* Fixing linting issues