The activated setup mode is indicated by the WLAN LED.

Co-authored-by: David Bauer <mail@david-bauer.net>

Ubiquiti UniFi AP PRO

Gone due to
commit 45c84a11 ("ar71xx: drop target")

Allow interface names to change on updates to handle hwconfig -> DSA and
similar migrations.

On devices with only a single interface, a sysconfig single_ifname is
created instead of wan_ifname or lan_ifname to allow separate
configuration in site.conf.

config_ifname was renamed to setup_ifname in Gluon v2015.1.

On PoE-powered devices, we usually want to use WAN for the setup mode.
As all outdoor devices are PoE-powered, we can reuse this function. This
switches the setup mode interface for new installations / after config
reset on a few devices that were missing in this list before.

Some files have received some additional refactoring.

This makes the LAN port the PoE master, so the AirGateway can be used to
supply power to another node connected via mesh-on-LAN.

Fixes #608

We also make use of the boolean support of simple-uci to make scripts
clearer.

Closes #844

The interfaces were accidentially switched when the CPE210 was separated
from the CPE510 code.