Fix scheduled sorting/filtering bug on started and stopped views in rtorrent

[chros73]

New pull request, same content (see #451).

Fixes: #449
Refers to: chros73#3

It works like a charm, I'm using it for 8 days now with this massive view config (for rtorrent-ps).

Actually, the started view got a new meaning with this and pyroscope's idea of using last_active custom field:

• we can sort like this and it's pretty useful (like the active view)
• and now we can add the scheduled sort for it:

schedule2 = sort_started,12,20,((view.sort,started))