Make factory default interface assignment more flexible
At the moment only 1 set of specific device assignments for WAN+LAN can be in the factory default config.
For initial setup, and for disaster recovery, it is often a benefit to be able to install an image, boot it without needing to access the (serial or VGA) console, and connect to LAN to login and setup the system or restore a backup config.
If this process can happen on more varieties of hardware, IMHO that would be good.
Make the factory default startup look for various pairs of devices to assign to WAN/LAN:
em0 em1 - the 2.2 defaults
vr1 vr0 - the 2.1 defaults (works on an Alix)
re1 re2 - matches the WAN and LAN labelled case on an APU
suggest other combinations used by popular hardware setups...
If none of the pairs exist, then resort to the existing interface assignment on console.