Coinbase API V2/V3 Updates (#818)

* Converted CoinbaseAPI to V3

* Fixed formating. Removed Debug

* Update PlaceOrder - not fully tested.

* Updated

* Completed Trades WebSocket

* Removed unused Code for CoinbaseAPI,
Removed unneeded parsing from ExchangeAPIExtensions

* Final  WebSockets Updated

* Revert "Final  WebSockets Updated"

This reverts commit f7a8889.

* Final CoinbaseAPI changes.
Completed OrderParsing
Fully Test PlaceOrder
Additional Error Checking on WebSockets
Removed Unused functions
Separated constants into second file - creating partial class
General Code Cleanup

* Fixed Socket URL on Connect to new format

Author: neuMediaCrypto

src/ExchangeSharp/API/Exchanges/Coinbase/ExchangeCoinbaseAPI.cs

@@ -0,0 +1,34 @@
+namespace ExchangeSharp
+{
+	public sealed partial class ExchangeCoinbaseAPI 
+	{
+		private const string ADVFILL = "advanced_trade_fill";
+		private const string AMOUNT = "amount";
+		private const string ASKS = "asks";
+		private const string BIDS = "bids";
+		private const string BUY = "BUY";
+		private const string CURRENCY = "currency";
+		private const string CURSOR = "cursor";
+		private const string EVENTS = "events";
+		private const string LEVEL2 = "level2";
+		private const string MARKETTRADES = "market_trades";
+		private const string ORDERID = "order_id";
+		private const string ORDERS = "orders";
+		private const string PRICE = "price";
+		private const string PRICEBOOK = "pricebook";
+		private const string PRICEBOOKS = "pricebooks";
+		private const string PRICELEVEL = "price_level";
+		private const string PRODUCTID = "product_id";
+		private const string PRODUCTS = "products";
+		private const string SIDE = "side";
+		private const string SIZE = "size";
+		private const string STATUS = "status";
+		private const string SUBSCRIBE = "subscribe";
+		private const string TICKER = "ticker";
+		private const string TIME = "time";
+		private const string TRADEID = "trade_id";
+		private const string TRADES = "trades";
+		private const string TYPE = "type";
+		private const string VALUE = "value";
+	}
+}