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