Move project color editing to "Edit Details" from "Edit Icon"

Summary: Fixes T5482. This isn't perfect but seems less confusing/ugly on the balance.

Test Plan:
  - Edited color under "Edit Details".
  - Edited icon under "Edit Icon".
  - No weird submit button state issue.
  - No weird alignmnet issue.

Reviewers: chad

Reviewed By: chad

Subscribers: epriestley

Maniphest Tasks: T5482

Differential Revision: https://secure.phabricator.com/D9742