Fix extensions for python files
Clean up code and convert to python3

This commit cleans up the python code and converts it to work with
python3. Changes include
- Removing errant tabs
- Fixing various problems with exception and print syntax
Change lib/names to reflect dependency on python3 and LibreOffice
Rename files to match LO dependency
README: Update command-line examples

change ssconverter.py -> libreconverter.py