Project - add ability to select an icon for typeaheads and such

Summary: Fixes T5090. Introduced getIcon into Handle stack which allows you to specify a per handle icon. getIcon falls back ot getTypeIcon.

Test Plan: changed the icon on a project a bunch. verified transactions showed up. verified icon showed up in typeahead. verified icon showed up in tokens that were pre-generated (not typed in). units test passed.

Reviewers: chad, epriestley

Reviewed By: epriestley

Subscribers: epriestley, Korvin

Maniphest Tasks: T5090

Differential Revision: https://secure.phabricator.com/D9264