Add another compareRows() method based upon a full table scan, rather
than the PK Index scan, to track down a problem in Alter Table.
Fix bug in BasicDDLFunctions#alterTableRemoveOldStorage() which, if the
table/group was not changed, would delete the underlying group storage
under the assumption the AlterTable processing had moved it. 

Update tests to match.
merge tjoneslo: Fix alter table metadata lose data

Merge pull request #1412 from tjoneslo/sql-layer/fix-alter-table-metadata-lose-data
https://github.com/FoundationDB/sql-layer/pull/1412