Add -s option. Basic debug info is overlaid and written in debug.svg

This can easily help uncover the problematic cases.

ie. AC1540347 is not parsed well - only 18 records
are generated. This is easily demonstrated by running :

$ parse-geometric.py -d -s ceo-files/AC1540347.pdf -p 4 converted/AC1540347.xml

followed by

$ inkscape debug.svg
Bugfix : correct vcand2 comparison with hcand1. 30 records now in AC1540347.pdf