Melange IP address allocation polices

Melange should provide the ability to build policies where we can restrict usage of certain IPs in a block. The two initial mechanisms for doing this are driven from IP offsets and IP octets. Offsets just allow you to reserve the first x addresses in a block or the last y addresses. Octets are tied to specific final address octets such as xxx.xxx.xxx.1 or xxx.xxx.xxx.255. The octets are required because some blocks span multiple octet ranges. So, if you want to block .255 addresses from being allocated in a /20 block, for instance, you must use octets as opposed to offsets. These policies will only apply to IPv4 addresses.