Path: added Path.fromShapes and Path.sortWires

* 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.

src/Mod/Path/App/AppPath.cpp

@@ -88,4 +88,6 @@ PyMODINIT_FUNC initPath()
     Path::Area                   ::init();
     Path::FeatureArea            ::init();
     Path::FeatureAreaPython      ::init();
+    Path::FeatureAreaView        ::init();
+    Path::FeatureAreaViewPython  ::init();
 }