[GetMarketReport] Add volume granularity

[Janaka-Steph]

Add volume granularity in order to have a detailed report with all data points, from which we can draw a volume chart.

• GetMarketReport is called with an additional timeframe parameter of type TimeFrame.

• TimeFrame is a set of time frames commonly used in charting.

• MarketReport returns a new detail_volume array of MarketVolume.

• MarketVolume get new start_date and end_date specifying the covered time period. end_date could eventually be omitted since we can calculate this information from timeframe.

Please review @tiero @sekulicd @altafan

[Janaka-Steph]

Let me know if Granularity should be renamed TimeFrame (proper trading term) or Candle. The idea behind not using Candle is that the report could be used for something else than drawing a chart.

[tiero]

Let me know if Granularity should be renamed TimeFrame (proper trading term)

Prefer TimeFrame indeed