Adding toXYZ() and rotate() for polygons

[themmes]

#3 Polygon rotation
Simply copied the rotation function from the CSG class to work with a single polygon. This function is useful for triangulation of polygons. Most triangulation works in 2D, therefore it is sometimes necessary to random_rotate polygon if the polygon.plane is vertical.

toXYZ
There was not yet an option to retrieve coordinate values straight from the Polygon.