You have different ways to do that.
Via qgc, goto widget "calibration and parameters" and edit the CONFIG_VERSION number to 0.
But use only for editing the CONFIG_NUMBER this widget.
other one
create a empty params.txt file on your sd-card, insert #definne CONFIG_VERSION 0,
insert into aq-board, and reboot.
In the next release from the qgroundcontrol, I will do a button/menu for a factory reset.