Clean up CSS for Pholio upload thing
Summary: Ref T3572. Pure JS/CSS changes, just cleaning up some of the mess I made and slightly improving the behavior on mobile (you won't be able to edit images on mobile, but you could fix descriptions and titles, at least).
Test Plan: {F50887}
Reviewers: btrahan, chad
Reviewed By: btrahan
CC: aran
Maniphest Tasks: T3572
Differential Revision: https://secure.phabricator.com/D6500