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/Utility/TaskExtensions.cs

@@ -0,0 +1,99 @@
+// 
+// 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.Text;
+using System.Threading.Tasks;
+
+namespace Microsoft.SqlTools.Hosting.Utility
+{
+    public static class TaskExtensions
+    {
+        /// <summary>
+        /// Adds handling to check the Exception field of a task and log it if the task faulted
+        /// </summary>
+        /// <remarks>
+        /// This will effectively swallow exceptions in the task chain. 
+        /// </remarks>
+        /// <param name="antecedent">The task to continue</param>
+        /// <param name="continuationAction">
+        /// An optional operation to perform after exception handling has occurred
+        /// </param>
+        /// <returns>Task with exception handling on continuation</returns>
+        public static Task ContinueWithOnFaulted(this Task antecedent, Action<Task> continuationAction)
+        {
+            return antecedent.ContinueWith(task =>
+            {
+                // If the task hasn't faulted or has an exception, skip processing
+                if (!task.IsFaulted || task.Exception == null)
+                {
+                    return;
+                }
+                
+                LogTaskExceptions(task.Exception);
+
+                // Run the continuation task that was provided
+                try
+                {
+                    continuationAction?.Invoke(task);
+                }
+                catch (Exception e)
+                {
+                    Logger.Instance.Write(LogLevel.Error, $"Exception in exception handling continuation: {e}");
+                    Logger.Instance.Write(LogLevel.Error, e.StackTrace);
+                }
+            });
+        }
+
+        /// <summary>
+        /// Adds handling to check the Exception field of a task and log it if the task faulted.
+        /// This version allows for async code to be ran in the continuation function.
+        /// </summary>
+        /// <remarks>
+        /// This will effectively swallow exceptions in the task chain. 
+        /// </remarks>
+        /// <param name="antecedent">The task to continue</param>
+        /// <param name="continuationFunc">
+        /// An optional operation to perform after exception handling has occurred
+        /// </param>
+        /// <returns>Task with exception handling on continuation</returns>
+        public static Task ContinueWithOnFaulted(this Task antecedent, Func<Task, Task> continuationFunc)
+        {
+            return antecedent.ContinueWith(task =>
+            {
+                // If the task hasn't faulted or doesn't have an exception, skip processing
+                if (!task.IsFaulted || task.Exception == null)
+                {
+                    return;
+                }
+
+                LogTaskExceptions(task.Exception);
+
+                // Run the continuation task that was provided
+                try
+                {
+                    continuationFunc?.Invoke(antecedent).Wait();
+                }
+                catch (Exception e)
+                {
+                    Logger.Instance.Write(LogLevel.Error, $"Exception in exception handling continuation: {e}");
+                    Logger.Instance.Write(LogLevel.Error, e.StackTrace);
+                }
+            });
+        }
+
+        private static void LogTaskExceptions(AggregateException exception)
+        {
+            // Construct an error message for an aggregate exception and log it
+            StringBuilder sb = new StringBuilder("Unhandled exception(s) in async task:");
+            foreach (Exception e in exception.InnerExceptions)
+            {
+                sb.AppendLine($"{e.GetType().Name}: {e.Message}");
+                sb.AppendLine(e.StackTrace);
+            }
+            Logger.Instance.Write(LogLevel.Error, sb.ToString());
+        }
+    }
+}