Actively dispose of temporary files

[9382]

Recently changed the file system to avoid dangerous calls to Thread.sleep by using a dedicated temp/ directory and clearing it on restart, but this now means we form an (admittedly minor) build-up of files until what will hopefully be the next update. Something to actively clear these temporary files after a minute or few of existing would be nice, but by no means hugely important.

[ZeNyfh]

This is a very simply feature, I can do this now.