added isGaseous extension method to fueltype

VectoCommon/VectoCommon/Models/FuelType.cs

@@ -74,5 +74,16 @@ namespace TUGraz.VectoCommon.Models
 		{
 			return ftype.GetLabel();
 		}
+
+		public static bool IsGaseous(this FuelType ftype)
+		{
+			switch (ftype) {
+				case (FuelType.NGPI):
+				case (FuelType.NGCI):
+					return true;
+				default:
+					return false;
+			}
+		}
 	}
 }
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