重构LineChart和BarChart，移除Line和Bar组件，参数统一放到Serie中配置。

Scripts/UI/Utility/AxisPool.cs

@@ -0,0 +1,35 @@
+
+using System.Collections.Generic;
+
+namespace XCharts
+{
+    public static class XAxisPool
+    {
+        private static readonly ObjectPool<XAxis> s_ListPool = new ObjectPool<XAxis>(null, null);
+
+        public static XAxis Get()
+        {
+            return s_ListPool.Get();
+        }
+
+        public static void Release(XAxis toRelease)
+        {
+            s_ListPool.Release(toRelease);
+        }
+    }
+
+    public static class YAxisPool
+    {
+        private static readonly ObjectPool<YAxis> s_ListPool = new ObjectPool<YAxis>(null, null);
+
+        public static YAxis Get()
+        {
+            return s_ListPool.Get();
+        }
+
+        public static void Release(YAxis toRelease)
+        {
+            s_ListPool.Release(toRelease);
+        }
+    }
+}