Added a Disable Macros function that can be called in some contexts where Macros are unsuitable

Summary: Semi Fixed T2397

Test Plan: Can disable the meme button on manually toggling the class variable.

Reviewers: epriestley

Reviewed By: epriestley

CC: aran, Korvin

Maniphest Tasks: T2397

Differential Revision: https://secure.phabricator.com/D4781