Allow letters on address (local DNS name instead of IP)

[leoravagnani]

I have local DNS names for some of my devices so I don't have to worry if they change IP for whatever reason, which is great for Home Assistant.

I just had to change the IP on one of my TVs and had to delete the device and add it again with the new IP. If we were allowed to use letters this would not be an issue anymore (not that it's a big deal, but seemingly we are computer nerds haha).

Somewhat related, #6 was asking for device editing, which would also be nice to have.