Feature/system.text.json (#192)

Initial support for System.Text.Json and some refactoring

CryptoExchange.Net/Converters/MessageParsing/MessagePath.cs

@@ -0,0 +1,50 @@
+using System.Collections;
+using System.Collections.Generic;
+
+namespace CryptoExchange.Net.Converters.MessageParsing
+{
+    /// <summary>
+    /// Message access definition
+    /// </summary>
+    public struct MessagePath : IEnumerable<NodeAccessor>
+    {
+        private List<NodeAccessor> _path;
+
+        internal void Add(NodeAccessor node)
+        {
+            _path.Add(node);
+        }
+
+        /// <summary>
+        /// ctor
+        /// </summary>
+        public MessagePath()
+        {
+            _path = new List<NodeAccessor>();
+        }
+
+        /// <summary>
+        /// Create a new message path
+        /// </summary>
+        /// <returns></returns>
+        public static MessagePath Get()
+        {
+            return new MessagePath();
+        }
+
+        /// <summary>
+        /// IEnumerable implementation
+        /// </summary>
+        /// <returns></returns>
+        public IEnumerator<NodeAccessor> GetEnumerator()
+        {
+            for (var i = 0; i < _path.Count; i++)
+                yield return _path[i];
+        }
+
+        IEnumerator IEnumerable.GetEnumerator()
+        {
+            return GetEnumerator();
+        }
+    }
+}