Allow dynamic specification of Router ID

[robshakir]

jBGP currently expects that the BGP router id is hard-coded at either side, which is not typical for an implementation. Allow the router ID to be discovered dynamically + validate on the jBGP side.

16:54:23.015 [nioEventLoopGroup-2-1] ERROR c.j.o.b.n.h.ValidateServerIdentifier - expected remote BGP identifier 16843266, received BGP identifier 3232288642
16:54:23.019 [nioEventLoopGroup-2-1] DEBUG c.j.o.bgp.netty.handlers.BGPv4Codec - Sending: com.jive.oss.bgp.netty.protocol.open.BadBgpIdentifierNotificationPacket@61d97554[type=3,errorCode=2,errorSubcode=3]
16:54:23.020 [nioEventLoopGroup-2-1] DEBUG c.j.o.bgp.netty.handlers.BGPv4Codec - Received: com.jive.oss.bgp.netty.protocol.KeepalivePacket@46a0fda6[type=4