[charcoal/object] Add support for anonymizing IP address

[mcaskill]

For the UserData model, I propose we introduce a resolveIp() method similar to resolveOrigin() to allow integrations to customize the IP source.

Anonymization should be built into the IpProperty with support for controlling how much anonymity the address should have (for example, how many octects to anonymize from the end of an IPv4 address).