Shared API's V2 (#289)

Added V2 Shared API's infrastructure
Added request coalescing
Added rate limiting admission logic
Fixed some rate limiting issues

CryptoExchange.Net/SharedApis/Models/SharedFundingFee.cs

@@ -0,0 +1,51 @@
+using System;
+using System.Diagnostics;
+
+namespace CryptoExchange.Net.SharedApis
+{
+    /// <summary>
+    /// Funding fee payment
+    /// </summary>
+    [DebuggerDisplay("[{Timestamp}] {Symbol,nq} {Fee} {Asset,nq}")]
+    public record SharedFundingFee
+    {
+        /// <summary>
+        /// Id
+        /// </summary>
+        public string? Id { get; set; }
+
+        /// <summary>
+        /// The symbol
+        /// </summary>
+        public string Symbol { get; set; }
+
+        /// <summary>
+        /// The asset the funding fee was paid in
+        /// </summary>
+        public string? Asset { get; set; }
+
+        /// <summary>
+        /// The funding fee paid
+        /// </summary>
+        public decimal Fee { get; set; }
+        /// <summary>
+        /// Timestamp
+        /// </summary>
+        public DateTime Timestamp { get; set; }
+
+        /// <summary>
+        /// The side of the position
+        /// </summary>
+        public SharedPositionSide? Side { get; set; }
+
+        /// <summary>
+        /// ctor
+        /// </summary>
+        public SharedFundingFee(string symbol, decimal fee, DateTime timestamp)
+        {
+            Symbol = symbol;
+            Fee = fee;
+            Timestamp = timestamp;
+        }
+    }
+}