Added date range to global cache

MarketDataLib/Cache/GBPriceCache.cs

@@ -133,6 +133,22 @@ namespace MarketData.Cache
         return pricesByDate[date];
       }
     }
+
+    public Prices GetPrices(String symbol, DateTime earlierDate, DateTime laterDate)
+    {
+      DateGenerator dateGenerator = new DateGenerator();
+
+      if(laterDate<earlierDate)
+      {
+        DateTime tempDate = earlierDate;
+        earlierDate = laterDate;
+        laterDate=tempDate;
+      }
+      List<DateTime> datesList = dateGenerator.GenerateHistoricalDates(earlierDate, laterDate);
+      datesList = datesList.Where(x => x >= earlierDate).ToList();
+      return GetPrices(symbol, laterDate, datesList.Count);
+    }
+
 // The most recent price is returned at the lowest index
     public Prices GetPrices(String symbol,DateTime startDate,int dayCount)
     {