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

test/Microsoft.SqlTools.Hosting.UnitTests/ProtocolTests/RequestContextTests.cs

@@ -0,0 +1,97 @@
+//
+// 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.Collections.Concurrent;
+using Microsoft.SqlTools.Hosting.Contracts.Internal;
+using Microsoft.SqlTools.Hosting.Protocol;
+using Xunit;
+
+namespace Microsoft.SqlTools.Hosting.UnitTests.ProtocolTests
+{
+    public class RequestContextTests
+    {   
+        #region Send Tests
+
+        [Fact]
+        public void SendResult()
+        {
+            // Setup: Create a blocking collection to collect the output
+            var bc = new BlockingCollection<Message>(new ConcurrentQueue<Message>());
+            
+            // If: I write a response with the request context
+            var rc = new RequestContext<CommonObjects.TestMessageContents>(CommonObjects.RequestMessage, bc);
+            rc.SendResult(CommonObjects.TestMessageContents.DefaultInstance);
+
+            // Then: The message writer should have sent a response
+            Assert.Equal(1, bc.ToArray().Length);
+            Assert.Equal(MessageType.Response, bc.ToArray()[0].MessageType);
+        }
+
+        [Fact]
+        public void SendEvent()
+        {
+            // Setup: Create a blocking collection to collect the output
+            var bc = new BlockingCollection<Message>(new ConcurrentQueue<Message>());
+            
+            // If: I write an event with the request context
+            var rc = new RequestContext<CommonObjects.TestMessageContents>(CommonObjects.RequestMessage, bc);
+            rc.SendEvent(CommonObjects.EventType, CommonObjects.TestMessageContents.DefaultInstance);
+            
+            // Then: The message writer should have sent an event
+            Assert.Equal(1, bc.ToArray().Length);
+            Assert.Equal(MessageType.Event, bc.ToArray()[0].MessageType);
+        }
+
+        [Fact]
+        public void SendError()
+        {
+            // Setup: Create a blocking collection to collect the output
+            const string errorMessage = "error";
+            const int errorCode = 123;
+            var bc = new BlockingCollection<Message>(new ConcurrentQueue<Message>());
+            
+            // If: I write an error with the request context
+            var rc = new RequestContext<CommonObjects.TestMessageContents>(CommonObjects.RequestMessage, bc);
+            rc.SendError(errorMessage, errorCode);
+            
+            // Then: 
+            // ... The message writer should have sent an error
+            Assert.Equal(1, bc.ToArray().Length);
+            Assert.Equal(MessageType.ResponseError, bc.ToArray()[0].MessageType);
+            
+            // ... The error object it built should have the reuired fields set
+            var contents = bc.ToArray()[0].GetTypedContents<Error>();
+            Assert.Equal(errorCode, contents.Code);
+            Assert.Equal(errorMessage, contents.Message);
+        }
+
+        [Fact]
+        public void SendException()
+        {
+            // Setup: Create a blocking collection to collect the output
+            var bc = new BlockingCollection<Message>(new ConcurrentQueue<Message>());
+            
+            // If: I write an error as an exception with the request context
+            const string errorMessage = "error";
+            var e = new Exception(errorMessage);
+            var rc = new RequestContext<CommonObjects.TestMessageContents>(CommonObjects.RequestMessage, bc);
+            rc.SendError(e);
+            
+            // Then: 
+            // ... The message writer should have sent an error
+            Assert.Equal(1, bc.ToArray().Length);
+            Assert.Equal(MessageType.ResponseError, bc.ToArray()[0].MessageType);
+            
+            // ... The error object it built should have the reuired fields set
+            var contents = bc.ToArray()[0].GetTypedContents<Error>();
+            Assert.Equal(e.HResult, contents.Code);
+            Assert.Equal(errorMessage, contents.Message);
+            
+        }
+        
+        #endregion
+    }
+}