Minor Timeline CSS tweaks

Summary: Remove user image background color, fix spacing in titles.

Test Plan: Tested a task and a pholio mock, various states.

Reviewers: epriestley, btrahan

Reviewed By: epriestley

CC: Korvin, aran

Differential Revision: https://secure.phabricator.com/D7190
Add `bin/policy unlock`

Summary: Ref T603. We might need a fine-grained CLI tool later on, but here's a bat we can bludgeon things with.

Test Plan:
  - Ran `bin/policy unlock D12` (adjusted policies).
  - Ran `bin/policy unlock rPca85c457ebcb` (got "not mutable" stuff).

Reviewers: btrahan

Reviewed By: btrahan

CC: aran

Maniphest Tasks: T603

Differential Revision: https://secure.phabricator.com/D7189
Write "attach" edges when files are attached to objects via comment or other transactions

Summary: Ref T603. When a user comments on an object with an embedded file, write an "attached" edge.

Test Plan: Made a comment on a task with an embedded file, verified the edge was written in Files.

Reviewers: btrahan

Reviewed By: btrahan

CC: aran

Maniphest Tasks: T603

Differential Revision: https://secure.phabricator.com/D7191