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

src/Microsoft.SqlTools.ServiceLayer/EditData/UpdateManagement/RowCreate.cs

@@ -122,6 +122,26 @@ namespace Microsoft.SqlTools.ServiceLayer.EditData.UpdateManagement
             return command;
         }
 
+        /// <summary>
+        /// Generates a edit row that represents a row pending insertion
+        /// </summary>
+        /// <param name="cachedRow">Original, cached cell contents. (Should be null in this case)</param>
+        /// <returns>EditRow of pending update</returns>
+        public override EditRow GetEditRow(DbCellValue[] cachedRow)
+        {
+            // Iterate over the new cells. If they are null, generate a blank value
+            DbCellValue[] editCells = newCells.Select(cell => cell == null
+                    ? new DbCellValue {DisplayValue = string.Empty, IsNull = false, RawObject = null}
+                    : cell.AsDbCellValue)
+                .ToArray();
+            return new EditRow
+            {
+                Id = RowId,
+                Cells = editCells,
+                State = EditRow.EditRowState.DirtyInsert
+            };
+        }
+
         /// <summary>
         /// Generates the INSERT INTO statement that will apply the row creation
         /// </summary>