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/RowDelete.cs

@@ -9,6 +9,7 @@ using System.Globalization;
 using System.Threading.Tasks;
 using Microsoft.SqlTools.ServiceLayer.EditData.Contracts;
 using Microsoft.SqlTools.ServiceLayer.QueryExecution;
+using Microsoft.SqlTools.ServiceLayer.QueryExecution.Contracts;
 using Microsoft.SqlTools.Utility;
 
 namespace Microsoft.SqlTools.ServiceLayer.EditData.UpdateManagement
@@ -72,6 +73,24 @@ namespace Microsoft.SqlTools.ServiceLayer.EditData.UpdateManagement
             return command;
         }
 
+        /// <summary>
+        /// Generates a edit row that represents a row pending deletion. All the original cells are
+        /// intact but the state is dirty.
+        /// </summary>
+        /// <param name="cachedRow">Original, cached cell contents</param>
+        /// <returns>EditRow that is pending deletion</returns>
+        public override EditRow GetEditRow(DbCellValue[] cachedRow)
+        {
+            Validate.IsNotNull(nameof(cachedRow), cachedRow);
+
+            return new EditRow
+            {
+                Id = RowId,
+                Cells = cachedRow,
+                State = EditRow.EditRowState.DirtyDelete
+            };
+        }
+
         /// <summary>
         /// Generates a DELETE statement to delete this row
         /// </summary>