Proof of concept how a real reload-handling with systemd could work.

Refs #6118
Only rewrite pidfile when reloading was successful.

Refs #6118
Unlink the pidfile when we really shutdown (not reload).

Refs #6118
Don't fork twice on daemon reload but still take care of setting up correct IO file descriptors.

Refs #6118
Make sure the daemon wrote it's pidfile before the forking process exits.

Refs #6118
Fix coding style and C-string access

Refs #6118
Add Process::GetPID and make it work on Unix and Windows.

Refs #6118
Fix coding-style and use the "String"-class.

Refs #6118