IPv4/IPv6 utilities routine to move to a common place

following https://git.opendaylight.org/gerrit/#/c/60277/, there is a need to have a common place to handle IPv4/IPv6 addresses and prefixes in ODL.

Sridhar found some existing utils in [1] and [2]. We should eventually have them all in [1] so we pull utils from genius.

[1] https://github.com/opendaylight/genius/blob/stable/carbon/mdsalutil/mdsalutil-api/src/main/java/org/opendaylight/genius/mdsalutil/NWUtil.java#L180

[2] https://github.com/opendaylight/netvirt/blob/stable/carbon/vpnservice/aclservice/impl/src/main/java/org/opendaylight/netvirt/aclservice/utils/AclServiceUtils.java#L609