R1:8c01cc97f42b

Implement macros search by flags.

Summary: Reuse the existing flags functionality for searching macros. Currently implemented as a simple select element (for color).

Test Plan: Flagged some macros and tried searching by them.

Reviewers: epriestley

Reviewed By: epriestley

CC: aran, Korvin

Differential Revision: https://secure.phabricator.com/D6709