Docs updates

This MR introduces a number of updates to the documentation:

• It adds the Parametrization section and the GeoSerialTransformer from the original Geometry Kernel documentation

• I have compared the current documentation, which has been ported from the original Geometry Kernel documentation, and the output of the Doxygen docs over GeoModelKernel and noticed that a number of GeoShape nodes are missing from the documentation. Therefore, I have added them to the list of Shapes in the Kernel reference, and they will have to be documented later.

• I also added links to Shape nodes to the dedicated page. For those shapes for which a dedicated page is missing, no link has been created, which helps in identifying the shapes that needs to be documented:

https://geomodel.web.cern.ch/home/components/kernel/reference/#shapes

• I have ported the "Actions" section from the original documentation

• I have ported the "Base Classes for Subsystem Description" section from the original documentation

• I have ported the Appendix section from the original documentation

• I also have fixed the footnotes and the references

documentation/docs/components/kernel/overview/MaterialGeometry.md

@@ -46,6 +46,8 @@ The materials are then used to together with shapes to form logical volumes, dis
 
 Shapes are created using the new operator. Essentially, shapes within this system are required to store and provide access to the geometrical constants that describe their geometrical form. This data is, insofar as possible, to be specified on the constructor.
 
+Shapes are extensible and custom shapes can be built.
+
 Here is how one builds a box:
 
 ```cpp