Notify user if ENS domain resolution changes

[rekmarks]

Per the recommendation of the ENS team, we should notify users if the resolved address from an ENS name changes.

Prerequisites:

• ENS controller: Add EnsController core#151
• Integrate ENS controller with extension: PR TBD
  • Beyond simply adding the latest version of gaba to the extension, we will replace all ENS name validation/normalization with the function now exposed by gaba.

How we warn the user in the UI is an open question.

[Gudahtt]

Which ENS domains is this regarding? Any in the address book?

[rekmarks]

I would assume so, yes.