ipsec, allow using different source subnets for natting a ipsec connection, including 0.0.0.0/0

-ipsec, allow using different source subnets for natting a ipsec connection, including 0.0.0.0/0
-utils, new function get_subnet_usable_range($ip, $bits), returns the usable IP's in a subnet
-use the new function on dhcp pages