Add support to nominate prefix as remote address

[dmulyalin]

Is your feature request related to a problem? Please describe.
Many vendors support dynamic BGP peering by specifying prefix as a neighbor instead of a specific IP address, would be good to add support to document this using bgp plugin

Describe the solution you'd like
Add support to use prefix as remote address.

Describe alternatives you've considered
Alternative is to create prefix, set it to is a poll and create network broadcast ip, and use that ip as a remote address, this is a workaround, a more concise approach would be to add support to use prefix object as remote address.