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/IServiceHost.cs

@@ -0,0 +1,31 @@
+//
+// Copyright (c) Microsoft. All rights reserved.
+// Licensed under the MIT license. See LICENSE file in the project root for full license information.
+//
+
+using System;
+using System.Threading.Tasks;
+using Microsoft.SqlTools.DataProtocol.Contracts;
+using Microsoft.SqlTools.Hosting.Protocol;
+
+namespace Microsoft.SqlTools.Hosting
+{
+    /// <summary>
+    /// Interface for service hosts. Inherits interface requirements for JSON RPC hosts
+    /// </summary>
+    public interface IServiceHost : IJsonRpcHost
+    {
+        /// <summary>
+        /// Registers a task to be executed when the initialize event is received
+        /// </summary>
+        /// <param name="initializeCallback">Function to execute when the initialize event received</param>
+        void RegisterInitializeTask(Func<InitializeParameters, IEventSender, Task> initializeCallback);
+
+        /// <summary>
+        /// Registers a task to be executed when the shutdown event is received, before the channel
+        /// is closed
+        /// </summary>
+        /// <param name="shutdownCallback">Function to execute when the shutdown request is received</param>
+        void RegisterShutdownTask(Func<object, IEventSender, Task> shutdownCallback);
+    }
+}