adds null-value definition in VOTable for Long and Integer columns

      new ColumnInfo( "access_url",     String.class, "Access URL" ),

      new ColumnInfo( "access_format",  String.class, "Format (MIME type)" ),

      new ColumnInfo( "access_estsize", Long.class,   "Extimated size (KB)" ),

      genLongWithNullColInfo("access_estsize", "Extimated size (KB)" ),

      new ColumnInfo( "target_name", String.class,  "Target" ),