message: Put warnings at top with errors in the list
  If "Entries with errors first" is selected, put items with errors at
  the top, followed by warnings, followed by the rest. Previously
  warnings weren't sorted as "less severe errors", but they arguably
  should.
diff: @@ -118,6 +118,11 @@ bool CatalogItemsComparator::operator()(int i, int j) const
  if ( m_order.errorsFirst )
  {
  + if ( a.HasIssue() && !b.HasIssue() )
  + return true;
  + else if ( !a.HasIssue() && b.HasIssue() )
  + return false;
  +
  if ( a.HasError() && !b.HasError() )
  return true;
  else if ( !a.HasError() && b.HasError() )
  