Allow Almanac bindings to be disabled and unused interfaces to be removed

Summary:
Fixes T9762. Ref T10246.

Disabling Bindings: Previously, there was no formal way to disable bindings. The internal callers sometimes check some informal property on the binding, but this is a common need and deserves first-class support in the UI. Allow bindings to be disabled.

Deleting Interfaces: Previously, you could not delete interfaces. Now, you can delete unused interfaces.

Also some minor cleanup and slightly less mysterious documentation.

Test Plan: Disabled bindings and deleted interfaces.

Reviewers: chad

Reviewed By: chad

Subscribers: yelirekim

Maniphest Tasks: T9762, T10246

Differential Revision: https://secure.phabricator.com/D15345