Allow BGP Community

[shthead]

Add an option to let routes specify a BGP community (or communities) to be advertised.

[tbaschak]

👍 to this for sure. I've just run into this with a test anycast deployement and was looking at the source to see if any support existed so far.

[tbaschak]

I did a little hacking (just to force sending 1 community for now) and while I haven't had to withdraw yet (didn't code that, not sure that its actually needed there either though) it is working for my test ipv6 anycasted prefixes.