sqm-scripts: Fix a minor bug, add copyrights, improve logging

Changes committed to the cerowrt original repo after the initial import here:
 - Better license & copyright statements, as requested
 - Fixed a minor bug in stopping sqm
 - Logging improvements
 - Dead code removed
 - Typos corrected

Matches original version https://github.com/dtaht/ceropackages-3.10/commit/caf457283865fc894a7699dbcea89be4611d2e81 except that I bumped the version number.

Signed-off-by: Hannu Nyman <hannu.nyman@iki.fi>