Feature: Writing Execute Results to Temp File (#35)

* WIP for buffering in temporary file

* Adding support for writing to disk for buffering

* WIP - Adding file reader, factory for reader/writer

* Making long list use generics and implement IEnumerable

* Reading/Writing from file is working

* Removing unused 'skipValue' logic

* More tweaks to file buffer

Adding logic for cleaning up the temp files
Adding fix for empty/null column names

* Adding comments and cleanup

* Unit tests for FileStreamWrapper

* WIP adding more unit tests, and finishing up wiring up the output writers

* Finishing up initial unit tests

* Fixing bugs with long fields

* Squashed commit of the following:

commit df0ffc12a46cb286d801d08689964eac08ad71dd
Author: Benjamin Russell <beruss@microsoft.com>
Date:   Wed Sep 7 14:45:39 2016 -0700

    Removing last bit of async for file writing.

    We're seeing a 8x improvement of file write speeds!

commit 08a4b9f32e825512ca24d5dc03ef5acbf7cc6d94
Author: Benjamin Russell <beruss@microsoft.com>
Date:   Wed Sep 7 11:23:06 2016 -0700

    Removing async wrappers

* Rolling back test code for Program.cs

* Changes as per code review

* Fixing broken unit tests

* More fixes for codereview

src/Microsoft.SqlTools.ServiceLayer/QueryExecution/DataStorage/ServiceBufferFileStreamFactory.cs

@@ -0,0 +1,64 @@
+//
+// Copyright (c) Microsoft. All rights reserved.
+// Licensed under the MIT license. See LICENSE file in the project root for full license information.
+//
+
+using System.IO;
+
+namespace Microsoft.SqlTools.ServiceLayer.QueryExecution.DataStorage
+{
+    /// <summary>
+    /// Factory that creates file reader/writers that process rows in an internal, non-human readable file format
+    /// </summary>
+    public class ServiceBufferFileStreamFactory : IFileStreamFactory
+    {
+        /// <summary>
+        ///  Creates a new temporary file
+        /// </summary>
+        /// <returns>The name of the temporary file</returns>
+        public string CreateFile()
+        {
+            return Path.GetTempFileName();
+        }
+
+        /// <summary>
+        /// Creates a new <see cref="ServiceBufferFileStreamReader"/> for reading values back from
+        /// an SSMS formatted buffer file
+        /// </summary>
+        /// <param name="fileName">The file to read values from</param>
+        /// <returns>A <see cref="ServiceBufferFileStreamReader"/></returns>
+        public IFileStreamReader GetReader(string fileName)
+        {
+            return new ServiceBufferFileStreamReader(new FileStreamWrapper(), fileName);
+        }
+
+        /// <summary>
+        /// Creates a new <see cref="ServiceBufferFileStreamWriter"/> for writing values out to an
+        /// SSMS formatted buffer file
+        /// </summary>
+        /// <param name="fileName">The file to write values to</param>
+        /// <param name="maxCharsToStore">The maximum number of characters to store from long text fields</param>
+        /// <param name="maxXmlCharsToStore">The maximum number of characters to store from xml fields</param>
+        /// <returns>A <see cref="ServiceBufferFileStreamWriter"/></returns>
+        public IFileStreamWriter GetWriter(string fileName, int maxCharsToStore, int maxXmlCharsToStore)
+        {
+            return new ServiceBufferFileStreamWriter(new FileStreamWrapper(), fileName, maxCharsToStore, maxXmlCharsToStore);
+        }
+
+        /// <summary>
+        /// Disposes of a file created via this factory
+        /// </summary>
+        /// <param name="fileName">The file to dispose of</param>
+        public void DisposeFile(string fileName)
+        {
+            try
+            {
+                FileStreamWrapper.DeleteFile(fileName);
+            }
+            catch
+            {
+                // If we have problems deleting the file from a temp location, we don't really care
+            }
+        }
+    }
+}