IPsec: add virtual IPv6 pool for mobile clients
IPsec: add virtual IPv6 pool for mobile clients

This commit deals with ipsec.conf file drafting. In terms of mobile clients option 'rightsourceip' now may be:
1) empty if no pools are configured;
2) %pool_address%/%pool_netbits% for an IPv4 only option;
3) %pool_address_v6%/%pool_netbits_v6% for an IPv6 only option;
4) %pool_address%/%pool_netbits%,%pool_address_v6%/%pool_netbits_v6% for a dual stack option.
opnsense/core,opnsense/core,opnsense/core,opnsense/core,opnsense/core,opnsense/core