\o deprecated in favor of \li, \returns doesn't exist.

activeTransfersChanged signal is emitted when a transfer is added to
or removed from the activeTransfers list.

This allows to avoid the overhead of fetching the full list of transfers
just to check if any of them is active.

::toString() with time pattern can use localized numbers, which
doesn't end up proper ISO-8601 format. Also as local time
the value was ambigous after timezone change.

Removed references to files, which are not in git.