Added tanks stat info operation and calculation tier and Wn7 operation

WotBlitzStatisticsPro.Logic/Calculations/TierHelper.cs

@@ -0,0 +1,28 @@
+using System.Collections.Generic;
+using WotBlitzStatisticsPro.DataAccess.Model.Accounts;
+
+namespace WotBlitzStatisticsPro.Logic.Calculations
+{
+    public static class TierHelper
+    {
+		public static void CalculateMiddleTier(this AccountInfoHistory account, IList<TankInfoHistory> allTanks, Dictionary<long, int> tankTires)
+        {
+            double x = 0d;
+            if (!account.Battles.HasValue)
+            {
+                return;
+            }
+            foreach (var tank in allTanks)
+            {
+                if (tankTires.ContainsKey(tank.TankId) && tank.Battles.HasValue && tank.Battles > 0)
+                {
+                    x += tankTires[tank.TankId] * tank.Battles.Value;
+                }
+            }
+            if (account.Battles > 0)
+                x /= account.Battles.Value;
+            account.AvgTier = x;
+        }
+
+	}
+}