Language Service diagnostics and autocomplete (#9)

* Merge master to dev (#4)

* Misc. clean-ups related to removing unneeded PowerShell Language Service code.
* Remove unneeded files and clean up remaining code.
* Enable file change tracking with Workspace and EditorSession.

* Setup standard src, test folder structure.  Add unit test project.

* Actually stage the deletes.  Update .gitignore

* Integrate SqlParser into the onchange diagnostics to provide error messages.

* Add tests for the language service diagnostics

* Initial implementation for autocomplete.

* Switch to using sys.tables for autocomplete
Move some code into a better class

* Delete unused csproj file.

* Add nuget.config to pickup SQL Parser nuget package

test/ServiceHost.Test/Connection/ConnectionServiceTests.cs

@@ -0,0 +1,60 @@
+//
+// Copyright (c) Microsoft. All rights reserved.
+// Licensed under the MIT license. See LICENSE file in the project root for full license information.
+//
+
+using System.Threading.Tasks;
+using Microsoft.SqlTools.Test.Utility;
+using Xunit;
+
+namespace Microsoft.SqlTools.Test.Connection
+{
+    /// <summary>
+    /// Tests for the ServiceHost Connection Service tests
+    /// </summary>
+    public class ConnectionServiceTests
+    {
+        #region "Connection tests"
+
+        /// <summary>
+        /// Verify that the SQL parser correctly detects errors in text
+        /// </summary>
+        [Fact]
+        public void ConnectToDatabaseTest()
+        {
+            // connect to a database instance 
+            var connectionResult = 
+                TestObjects.GetTestConnectionService()
+                .Connect(TestObjects.GetTestConnectionDetails());
+
+            // verify that a valid connection id was returned
+            Assert.True(connectionResult.ConnectionId > 0);
+        }
+
+        /// <summary>
+        /// Verify that the SQL parser correctly detects errors in text
+        /// </summary>
+        [Fact]
+        public void OnConnectionCallbackHandlerTest()
+        {
+            bool callbackInvoked = false;
+
+            // setup connection service with callback
+            var connectionService = TestObjects.GetTestConnectionService();
+            connectionService.RegisterOnConnectionTask(
+                (sqlConnection) => { 
+                    callbackInvoked = true;
+                    return Task.FromResult(true); 
+                }
+            );
+            
+            // connect to a database instance 
+            var connectionResult = connectionService.Connect(TestObjects.GetTestConnectionDetails());
+
+            // verify that a valid connection id was returned
+            Assert.True(callbackInvoked);
+        }
+
+        #endregion
+    }
+}