Add KCM example
This is an import from the docs.plasma-mobile.org website with the following improvements:
- compilable in standalone mode (
cd content/docs/configuration/kcm; mkdir build; cmake .....; make -j8 install
- add instruction to run the kcm
- use KQuickAddons::ManagedConfigModule (theorically useless in this usecase)
This was mentioned in docs-plasma-mobile-org#13
Edited by Carl Schwan