Adds the capability to specify either an ip4, ip6, or both bind addresses instead of just a single bind address
By specifying the addresses to bind to, this sets the IPMode (either ip4, ip6, or both).
Based on the specified IPMode, several things happen:
a udp4 socket and/or a udp6 socket are opened
discovered peers will be contacted based on the proper entry in their enr (either ip+udp or ip6+udp6) (ip6 is the default in the case of the 'both' IPMode) using the proper socket
Resolves #167
IPMode(either ip4, ip6, or both).IPMode, several things happen: