* Add UML diagram
* Description of metaclasses
* Clarify that there are two constraint services

Issue-Ref: 3401
Issue-Url: https://af3-developer.fortiss.org/issues/3401



Signed-off-by: Simon Barner <barner@fortiss.org>

* Introduction copied from:
https://af3-developer.fortiss.org/projects/autofocus3/wiki/Tooling_Kernel_Concepts_and_Services
* Details copied from: package.htmls

Issue-Ref: 3401
Issue-Url: https://af3-developer.fortiss.org/issues/3401



Signed-off-by: Simon Barner <barner@fortiss.org>

Issue-Ref:3427
Signed-off-by: Hernan Ponce de Leon <ponce@fortiss.org>