Layout::Document.save: 'BackUp' Argument Needed

[3dmod]

Layout::Document.save always creates a 'Backup' file when saving an existing file.

There are circumstances that you do not want a 'Backup' saved which is why the 'Backup' Boolean argument is needed.

For example Scrapbook directories read 'Backup' files and clutter the Scrapbook list.

Being default to true would not break any existing code and add the needed argument.