Core: Add App::LocalCoordinateSystem.

Most of App::Origin is moved into this sub class of App::Origin.
Add App::Point. Change graphics of the planes/axis.
Remove scale-by-content behavior and make it fixed size on screen.

src/App/Graphviz.cpp

@@ -312,7 +312,10 @@ void Document::exportGraphviz(std::ostream& out) const
                 }
                 if (!sgraph) {
                     if (docObj->isDerivedFrom(DatumElement::getClassTypeId())) {
-                        sgraph = GraphList[static_cast<DatumElement*>(docObj)->getOrigin()];
+                        auto* lcs = static_cast<DatumElement*>(docObj)->getLCS();
+                        if (lcs) {
+                            sgraph = GraphList[lcs];
+                        }
                     }
                 }
             }