Progressive Results Part 2: Result Completion Event (#134)

The main change in this pull request is to add a new event that will be fired upon completion of a resultset but before the completion of a batch. This event will only fire if a resultset is available and generated.

Changes:
* ConnectionService - Slight changes to enable mocking, cleanup 
* Batch - Moving summary generation into ResultSet class, adding generation of ordinals for resultset and locking of result set list (which needs further refinement, but would be outside scope of this change)
* Adding new event and associated parameters for completion of a resultset. Params return the resultset summary
* Adding logic for assigning the event a handler in the query execution service
* Adding unit tests for testing the new event /making sure the existing tests work
* Refactoring some private properties into member variables

* Refactor to remove SectionData class in favor of BufferRange

* Adding callback for batch completion that will let the extension know that a batch has completed execution

* Refactoring to make progressive results work as per async query execution

* Allowing retrieval of batch results while query is in progress

* reverting global.json, whoops

* Adding a few missing comments, and fixing a couple code style bugs

* Using SelectionData everywhere again

* One more missing comment

* Adding new notification type for result set completion

* Plumbing event for result set completion

* Unit tests for result set events

This includes a fairly substantial change to create a mock of the
ConnectionService and to create separate memorystream storage arrays. It
preserves more correct behavior with a integration test, fixes an issue
where the test db reader will return n-1 rows because the Reliable
Connection Helper steals a record.

* Adding locking to ResultSets for thread safety

* Adding/fixing unit tests

* Adding batch ID to result set summary

test/Microsoft.SqlTools.ServiceLayer.Test/QueryExecution/DisposeTests.cs

@@ -28,7 +28,7 @@ namespace Microsoft.SqlTools.ServiceLayer.Test.QueryExecution
             var mockDataReader = Common.CreateTestConnection(null, false).CreateCommand().ExecuteReaderAsync().Result;
             
             // If: I setup a single resultset and then dispose it
-            ResultSet rs = new ResultSet(mockDataReader, mockFileStreamFactory.Object);
+            ResultSet rs = new ResultSet(mockDataReader, Common.Ordinal, Common.Ordinal, mockFileStreamFactory.Object);
             rs.Dispose();
 
             // Then: The file that was created should have been deleted
@@ -101,6 +101,7 @@ namespace Microsoft.SqlTools.ServiceLayer.Test.QueryExecution
             // ... We need a query service
             var queryService = Common.GetPrimedExecutionService(null, true, false, workspaceService.Object);
 
+
             // If:
             // ... I execute some bogus query
             var queryParams = new QueryExecuteParams { QuerySelection = Common.WholeDocument, OwnerUri = Common.OwnerUri };