[from fork parent #11] Subscriptions shall use friendly names, NOT channel numbers!

[rgon]

See: chris-ritsen#11 (comment)
Implemented in chris-ritsen#35

According to Dante Controller's manual, friendly names are used for making subscriptions:

If a device or channel is renamed, Dante routing considers it to be a different device or channel. If a new
device or channel is then given the old name, Dante routing will route from the new device in place of the pre-
vious device.

(https://dev.audinate.com/GA/dante-controller/userguide/pdf/latest/AUD-MAN-DanteController-4.14.x-v1.1.pdf, page 21)

So for consistent behavior,

add_subscription should be using friendly_names when present