This fixes CQS violation from WSF_ROUTER.dispatch_and_return_handler (...): ? WSF_HANDLER
and related code, and this is more compliant with concurrency.
In addition, the WSF_ROUTER_SESSION can be enhanced in the future to answer more advanced needs.
The documentation is built only on demand.
A mapping entry can be hidden for the documentation
One can change the status code when building itself the WSF_ROUTER_SELF_DOCUMENTATION_MESSAGE
Added WSF_ROUTER_MAPPING.associated_resource
Added WSF_ROUTER_SELF_DOCUMENTATION_HANDLER and WSF_ROUTER_SELF_DOCUMENTATION_MESSAGE to provide a self documentation for WSF_ROUTER (for now, only HTML)