Draft: qt: introduce JSSortFilterProxyModel and remove ControlListFilter

This way we can filter any model we want with JS, therefore QML. It also reduces complexity because we do not need to manually connect signals. This is what I proposed initially, but it was accepted in its own way. Now that I found time for it, here is an alternative and in my opinion a better way.

Draft now because I should add a way to sensibly get the count.

Request review @chub.