yWriter file converter-v1.6.0

v1.6.0 New document formatting, general program improvement

It is highly advised to update to this version.

- Imported Scenes/chapters and manuscript documents now have three-line "* * *" scene dividers instead of single blank lines.
- *Replace scene dividers with blank lines* is added to the "Format" menu.
- Scene titles as comments at the beginning of the scenes in the manuscript and work in progress documents are written back to yWriter.
- Chapter titles in the manuscript, scene descriptions, part descriptions, and chapter descriptions documents are written back to yWriter.
- Generate temporary files in the user's temp folder.
- Improve the Python3 connection to the StarBasic macro (abandon the calling batch file).