Related to WB-664 Data normalization should be saved in file: Older versions...

Related to WB-664 Data normalization should be saved in file: Older versions of wb_view/wb_command will cease processing XML in the CaretVolumeExtension if an unexpected element is encountered.  WB-664 added metadata for VolumeFile for saving of the palette normalization mode.  When writing the CaretVolumeExtension, if the file metadata contains only one element that is the palette normalization mode's default value, do not write the metadata.  This will minimize any error message if a user tries to read a newer volume file containing metadata with an older version of wb_view/wb_command (and Caret5).