Add the interface guessing code like there is in perl (#228)

files/usr/lib/lua/aredn/hardware.lua

@@ -130,6 +130,20 @@ function hardware.get_iface_name(name)
     if intfname then
         return intfname
     end
+    -- Now we guess
+    if name == "lan" then
+        return "eth0"
+    end
+    if name == "wan" then
+        return "eth0.1"
+    end
+    if name == "wifi" then
+        return "wlan0"
+    end
+    if name == "dtdlink" then
+        return "eth0.2"
+    end
+    -- Maybe the board knows
     return hardware.get_board().network[name].ifname
 end