Use CamelCase headers in this module's own code
Simplify headers installation location
See teams/frameworks-devs/kf6-workboard#3 (comment 431683)
For PrisonScanner, we can go with the CamelCase include dir, since it hasn't been in a KF release yet, so no backwards compatibility.
Replicate the include dir layout in the builddir
So that e.g. #include <Prison/Prison> works at build time, the same way it should work when other modules include it.