feature/edit/subset (#283)

* Changing query/subset API to only use Result on success, Error on error

* Creating an interservice API for getting query result subsets

* Updates to subset API

* RowStartIndex is now long
* Output of query/subset is a 2D array of DbCellValue
* Adding LongSkip method to LongList to allow skipping ahead by longs
* Moving LongList back to ServiceLayer utilities. Move refactoring

* Stubbing out request for edit/subset

* Initial implementation of getting edit rows

* Unit tests for RowEdit and RowDelete .GetEditRow

* Fixing major bugs in LongList implementation, adding much more thorough tests

* Adding some more unit tests and fixes to make unit tests pass

* Fixing comment

test/Microsoft.SqlTools.ServiceLayer.UnitTests/EditData/ServiceIntegrationTests.cs

@@ -64,6 +64,8 @@ namespace Microsoft.SqlTools.ServiceLayer.UnitTests.EditData
             efv.Validate();
         }
 
+
+
         #endregion
 
         #region Dispose Tests
@@ -215,6 +217,36 @@ namespace Microsoft.SqlTools.ServiceLayer.UnitTests.EditData
             edit.Verify(e => e.SetCell(It.IsAny<int>(), It.IsAny<string>()), Times.Once);
         }
 
+        [Fact]
+        public async Task GetRowsSuccess()
+        {
+            // Setup: Create an edit data service with a session
+            // Setup: Create an edit data service with a session
+            var eds = new EditDataService(null, null, null);
+            var session = GetDefaultSession();
+            eds.ActiveSessions[Constants.OwnerUri] = session;
+
+            // If: I validly ask for rows
+            var efv = new EventFlowValidator<EditSubsetResult>()
+                .AddResultValidation(esr =>
+                {
+                    Assert.NotNull(esr);
+                    Assert.NotEmpty(esr.Subset);
+                    Assert.NotEqual(0, esr.RowCount);
+                })
+                .Complete();
+            await eds.HandleSubsetRequest(new EditSubsetParams
+            {
+                OwnerUri = Constants.OwnerUri,
+                RowCount = 10,
+                RowStartIndex = 0
+            }, efv.Object);
+
+            // Then:
+            // ... It should be successful
+            efv.Validate();
+        }
+
         [Theory]
         [InlineData(null, "table", "table")]            // Null owner URI
         [InlineData(Common.OwnerUri, null, "table")]    // Null object name