cli: enable to add community
cli: enable to add community

$ gobgp global rib add 10.0.0.0/24 community 100:100
$ gobgp global rib add 10.0.0.0/24 community 100
// well known
$ gobgp global rib add 10.0.0.0/24 community no-export
// use , to add multiple communities
$ gobgp global rib add 10.0.0.0/24 community 100:100,200:200

Signed-off-by: ISHIDA Wataru <15703620d0b11e835ab4f34ebf88f2f40cce783e@lab.ntt.co.jp>

a16/gobgp,Dipsingh/gobgp,fujita/gobgp,h-naoto/gobgp,Dipsingh/gobgp,j-kato/gobgp,fujita/gobgp,h-naoto/gobgp,osrg/gobgp,a16/gobgp,tamihiro/gobgp,tamihiro/gobgp,tamihiro/gobgp,osrg/gobgp,ishidawataru/gobgp,Dipsingh/gobgp,j-kato/gobgp,fujita/gobgp,fujita/gobgp,osrg/gobgp,a16/gobgp,osrg/gobgp,a16/gobgp,ishidawataru/gobgp,ramrunner/gobgp,j-kato/gobgp,YujiOshima/gobgp,tamihiro/gobgp,a16/gobgp,a16/gobgp,YujiOshima/gobgp,YujiOshima/gobgp,ramrunner/gobgp,ishidawataru/gobgp,a16/gobgp,h-naoto/gobgp,ramrunner/gobgp