feature request: add distance and area measurements

[lamisoft-42]

I'd like to have a feature that lets me measure distances and even better the area of a plot of land. Example: right click in google maps, then select "Entfernungen messen" (clearly in the German version, probably something like "measure distance" in the English version...). Then each left-click adds a polygon line and the tool displays the total distance. If the polygon is closed, the area is automatically calculated.