filecount never updated

[dmd]

According to the documentation the metric mercure.master.router.main.incoming.files reports "Number of received DICOM files waiting in the incoming folder".

I believe this is supposed to be implemented here: https://github.com/mercure-imaging/mercure/blob/686ea40adaaa5ca915f9b50c23abb04858c51cd0/router.py#L111

However, the variable filecount is initialized to 0 here: https://github.com/mercure-imaging/mercure/blob/686ea40adaaa5ca915f9b50c23abb04858c51cd0/router.py#L37

and then never updated anywhere else in all of mercure.