Statusline format

Change `OPTION_MAX_SIZE` to 1024 (length of default statusline's format is more than 512!).
Add `format_statusline` option.
Remove `status_fopts`. By the way, name `track_fopts` is a bit confusing now, because it has status' and albums' options.

Maybe go up to 4096 to be extra safe while we still use such buffers?