Robustify profile image controls ever so slightly

Summary: show project profile image on pertinent edit page. also add a "Use Default Image" checkbox for both project and user profiles. Also added a function for projects to get the profile picture to prevent some copy + paste action.

Test Plan: set my user profile and project profile image. clicked "Use Default Image" and got the default image back.

Reviewers: epriestley, floatinglomas

Reviewed By: floatinglomas

CC: aran, Korvin

Maniphest Tasks: T1307

Differential Revision: https://secure.phabricator.com/D2852