ZB.com: fix MarketSymbolMetatadata.IsActive (#442)

- fixes #441
- improve ExchangeTrade.ToString() readability
- rename Digifinex directory

Author: vslee

ExchangeSharp/API/Exchanges/Digifnex/ExchangeDigifinexAPI.cs renamed to ExchangeSharp/API/Exchanges/Digifinex/ExchangeDigifinexAPI.cs

@@ -97,6 +97,7 @@ protected override async Task<IEnumerable<ExchangeMarket>> OnGetMarketSymbolsMet
 				var amountScaleDecimals = (decimal)Math.Pow(0.1, amountScale);
 				symbols.Add(new ExchangeMarket()
 				{
+					IsActive = true, // ZB.com does not provide this info, assuming all are active
 					MarketSymbol = prop.Name,
 					BaseCurrency = split[0],
 					QuoteCurrency = split[1],

ExchangeSharp/API/Exchanges/ZBcom/ExchangeZBcomAPI.cs

@@ -65,8 +65,10 @@ public bool IsBuy
         public override string ToString()
         {
 			StringBuilder flagsSB = new StringBuilder();
-			flagsSB.Append((Flags & ExchangeTradeFlags.IsFromSnapshot) == ExchangeTradeFlags.IsFromSnapshot ? "snap:" : "");
-			flagsSB.Append((Flags & ExchangeTradeFlags.IsLastFromSnapshot) == ExchangeTradeFlags.IsLastFromSnapshot ? "last" : "");
+			if ((Flags & ExchangeTradeFlags.IsFromSnapshot) == ExchangeTradeFlags.IsFromSnapshot)
+				flagsSB.Append("snap");
+			if ((Flags & ExchangeTradeFlags.IsLastFromSnapshot) == ExchangeTradeFlags.IsLastFromSnapshot)
+				flagsSB.Append(":last");
 			return string.Format("{0:s},p:{1},a:{2},{3},id:{4},{5}", 
 				Timestamp, Price, Amount, IsBuy ? "Buy" : "Sell",
 				Id, flagsSB);