Add v2 of the Hosting Service and build nuget packages for it (#675)

* Port v2 of Hosting service to SqlToolsService
- Renamed project to .v2 so that existing hosted service isn't impacted
- Copied over the CoreServices project which contains ConnectionServiceCore and other reusable services for anything interacting with MSSQL
- Ported unit test project across and verified tests run.

* Nuget package support for reusable DLLs

* Use 1.1 version per Karl's suggestion

* Use correct license URL and project URL

* Use new SMO packages

src/Microsoft.SqlTools.Hosting.v2/Protocol/IEventSender.cs

@@ -0,0 +1,23 @@
+//
+// Copyright (c) Microsoft. All rights reserved.
+// Licensed under the MIT license. See LICENSE file in the project root for full license information.
+//
+
+using Microsoft.SqlTools.Hosting.Contracts;
+
+namespace Microsoft.SqlTools.Hosting.Protocol
+{
+    /// <summary>
+    /// Interface for objects that can send events via the JSON RPC channel
+    /// </summary>
+    public interface IEventSender
+    {
+        /// <summary>
+        /// Sends an event over the JSON RPC channel
+        /// </summary>
+        /// <param name="eventType">Configuration of the event to send</param>
+        /// <param name="eventParams">Parameters for the event to send</param>
+        /// <typeparam name="TParams">Type of the parameters for the event, defined in <paramref name="eventType"/></typeparam>
+        void SendEvent<TParams>(EventType<TParams> eventType, TParams eventParams);
+    }
+}