Add AlmanacBinding, to bind a service to an interface

Summary: Ref T5833. Allows you to bind a service (like `db.example.com`) to one or more interfaces (for example, to specify a pool with one read/write host and two read-only hosts). You can't configure which hosts have which properties yet, but you can add all the relevant interfaces to the service. Next diff will start supporting service, binding, and device properties like "is writable", "is active", etc., so that Almanac will be able to express operations like "change which database is writable", "disable writes", "bring a device down", etc.

Test Plan: See screenshots.

Reviewers: btrahan

Reviewed By: btrahan

Subscribers: epriestley

Maniphest Tasks: T5833

Differential Revision: https://secure.phabricator.com/D10745