Create option in admin UI to configure a remote link

[jonstout]

There are two options depending on if we support one or more remote links per physical port.

If it's not too hard to tease out the cloud connect stuff, we might be able to just use:

cloud_interconnect_type=nsi
cloud_interconnect_id=urn:ogf:network:domain=*:node=*:port=*:link=*

If we require support for multiple remote links, instead add an nsi_link table:

- nsi_link_id
- interface_id
- urn