IPv6: move assignPublicIp6Address() from NetworkManager to new Ipv6AddressManager

Don't want to involve IP address management code in NetworkManager.
IPv6: Verify if requested IPv4/IPv6 addresses are valid

Also rename NetUtils.isValidIPv6() to NetUtils.isValidIpv6()
IPv6: Make the IPv6 input all lowercase

To make them consistent.
IPv6: Update NetworkResponse and NicResponse
IPv6: Add vlan overlap checking
IPv6: Fix generated DUID-LL

Should be: 00:03:00:01 + <Mac>
IPv6: Add IPv6 address to router in /etc/hosts
Fix a bug in listHosts that returns wrong zoneId for host.
IPv6: Remove dualstack parameter from createNetworkCmd

We can tell if it's dual stack by looking into the startIp and startIpv6.
Removing the merge conflict statements from git.
IPv6: Rename public_ipv6_address to user_ipv6_address
IPv6: Disable untested features
IPv6: Fix missed AddressFormat in nic table
IPv6: Fix VlanIpRangeResponse
IPv6: Check startipv6, endipv6 and ip6Gateway with ip range
libvirt has bug to report storage stastics