SoftAp0 is created by the wifidog service:
wifidog-pre-startup.service
&
wifidog-gateway.service
https://github.com/rcn-ee/repos/blob/master/seeed-wificonfig-installer/suite/jessie/debian/wifidog_pre
And if like me you don't have a cell phone or other bluetooth device to configure the wlan0 interface, I have that figured out and documented here: https://www.ccoderun.ca/programming/2016-06-29_BBGW/index.html#wifi