supercontig length should be max(superctg_end) not length because occasionally...

supercontig length should be max(superctg_end) not length because occasionally supercontigs do not start at 1

misc-scripts/surgery/SeqStoreConverter/BasicConverter.pm

@@ -374,7 +374,7 @@ sub supercontig_to_seq_region {
 
   my $select_sth = $dbh->prepare
     ("SELECT superctg_name, " .
-     "MAX(superctg_end)-MIN(superctg_start)+1 AS length " .
+     "MAX(superctg_end) AS length " .
      "FROM $source.assembly " .
      "GROUP BY superctg_name");