R1:5d30b1b4fb13

Various highlights

Summary:
Highlight thumb for image user is currently viewing.
Highlight selection when user mouseovers it's inline(on side).

Test Plan: {F33990}

Reviewers: epriestley

Reviewed By: epriestley

CC: aran, Korvin

Maniphest Tasks: T2446

Differential Revision: https://secure.phabricator.com/D5134