Link scoped symbols

Summary:
Elements with class na are now linked to symbol lookup. The
context is passed if we got one. See D3214.

Test Plan: Load Diffusion. Examine DOM and click on things.

Reviewers: epriestley

Reviewed By: epriestley

CC: nh, aran, Korvin

Maniphest Tasks: T1602

Differential Revision: https://secure.phabricator.com/D3215