Add stub "harbormaster.build.edit" and "harbormaster.buildable.edit" API methods

Summary: Ref T13072. These don't do anything useful yet, but get the skeletons in.

Test Plan: Loaded documentation pages without fataling.

Subscribers: PHID-OPKG-gm6ozazyms6q6i22gyam

Maniphest Tasks: T13072

Differential Revision: https://secure.phabricator.com/D21695