* Path.fromShapes can now convert any number of shapes to Path with
optimzied travel distances. It internally uses Path.sortWires to
minimize travel distances, and also sort wires by its Z height in case
of sectioned wires.
* The above python function is impelmented in Path::Area class.
* Path::FeatureShape is rewrote to take advantage of these two
functions.
* Add Path::FeatureAreaView to partially display a Path::FeatureArea's
sections.
Zheng, Lei