Change highwaterField into an array containing 'name' and 'alias' elements. Needed in order to generate valid :criteria replacement

Change mssql.inc so that its fetch method replaces :criteria placeholder with either an idlist or a highwater or 1=1 depending on whether an idlist was passed inot the request. Needed for reprocessing needs_update=1 records on migrations that also use highwater ... Includes minor drush integration fix and table_copy plugin fix when the import has no records changed