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.Hosting/Utility/Validate.cs

@@ -37,9 +37,9 @@ namespace Microsoft.SqlTools.Utility
         /// <param name="upperLimit">The upper limit which the value should not be greater than.</param>
         public static void IsWithinRange(
             string parameterName,
-            int valueToCheck,
-            int lowerLimit, 
-            int upperLimit)
+            long valueToCheck,
+            long lowerLimit,
+            long upperLimit)
         {
             // TODO: Debug assert here if lowerLimit >= upperLimit