fixed https://github.com/jnweiger/inkscape-gears-dev/issues/20
V0.8: Added option to turn the undercut alert into console output.
The information it produces is valuable, but the console is not always visible to endusers.
But the confirming the alert *every time* can be annoying. Thus we allow the user to choose.
Fixed https://github.com/jnweiger/inkscape-gears-dev/issues/19 -- ring gears are now okay.