ubus: add command to create devices dynamically

[G10h4ck]

Some kind of devices might become available after initial configuration, and other one like WDS stations or APuP peers can create unpredictably many linux interfaces like wlan0.peer1 wlan0.peer2...

To use those linux interfaces as a base for other devices on top of those like 802.1ad devices we need to be able to create them at runtime ofter thos comes up, so an ubus command have been added for that.

ubus call network add_dynamic_device
'{"name":"NewDeviceName", "type":"8021ad",
"ifname":"wlan0.peer1", "vid":"47"}'

This will create the device that can be used for one or more interface with pre-existent commands

ubus call network add_dynamic
'{"name":"NewInterfaceName", "proto":"static", "auto":1,
"device":"NewDeviceName",
"ipaddr":"192.0.2.0", "netmask":"255.255.255.255"}' ubus call network.interface.NewInterfaceName up

To inspect the newly created device status a pre-existent command can be used

ubus call network.device status '{"name":"NewDeviceName"}'