==============================
Class for managing internal and external geometry as a single object. This is a light-weight alternative to
passing the whole SketchObject.
It reflects the format used in getCompleteGeometry of SketchObject and Sketch solver facade class, while providing
several convenient conversion functions to map indices.
Internal and external geometries are present in a single geometry vector one after the other.
The index of the geomlist (all layers) and the GeoId can be converted from each other at needed
using the member fuctions (and sometimes the static member functions).
Internal implementation is as a template GeoListModel<T>.
The following types are instantiated. Specialisation is provided where necessary.
GeoList = GeoListModel<Part::Geometry *>;
GeoListFacade = GeoListModel<std::unique_ptr<const Sketcher::GeometryFacade>>;
This enables to use the lighter GeoList were sufficient, while enabling off-the-shelf replacement
when switching to a GeoListFacade is necessary.
