Allow also scan of other areas

[Nudin]

I think this idea could be expanded to other types of areas as forests, Buildings and even roads.
For forests it would only need an configuration variable to set the tagging-scheme.
For buildings it would be nice to have a) an value to set the sensitivity higher at the red channel and b) an value witch makes the areas having more right angles.
For roads it would be nessesary to scan for one-dimension object and map them as ways
Would be nice if you'd integrate even some of this in future.