[Request] Hide watched videos only if older than a certain age

[BaconCatBug]

Mainly those over two weeks, but preferably a configurable amount. Youtube is completely broken and forces two week old videos to show even if you manually hide them. While I can hide them with the watched video filter, I'd want to keep more recent videos viewable as I often rewatch videos.

[Droyk]

Can be merged with #56 .