Path changes

* Relaxed valid base shape requirement, as long as it can return a
  shape using part.getShape()

* Improve ViewProviderPath performance by sharing the same selection
  observer

* Relocate libarea binary installation

src/Mod/Path/Gui/ViewProviderPath.h

@@ -42,8 +42,9 @@ class SoSwitch;
 namespace PathGui
 {
 
+class PathSelectionObserver;
+
 class PathGuiExport ViewProviderPath : public Gui::ViewProviderGeometryObject
-                                     , public Gui::SelectionObserver
 {
     PROPERTY_HEADER(PathGui::ViewProviderPath);
     typedef ViewProviderGeometryObject inherited;
@@ -78,14 +79,14 @@ public:
     virtual std::string getElement(const SoDetail *) const;
     SoDetail* getDetail(const char* subelement) const;
 
-    virtual void onSelectionChanged(const Gui::SelectionChanges& msg);
-
     void updateShowConstraints();
     void updateVisual(bool rebuild = false);
     void hideSelection();
 
     virtual void showBoundingBox(bool show);
 
+    friend class PathSelectionObserver;
+
 protected:
 
     virtual void onChanged(const App::Property* prop);