[GRASS5] v.to.db 2 new features compactness and perimeter

[Hamish]

> > > I fixed my fix for supporting compactness in v.to.db. I also added
> > > support for perimeter option which calculates the perimeter of an
> > > area. Compactness is calculated by doing:


should we add a warning to the help page about the fractal depth
problem? We wouldn't want people to trust the answers in error if they
start comparing different datasets. Maybe that is what compactness is
partly used as a measure of?



Hamish