Project - use hashtag as a way to access project profile in URI, e.g. /project/hashtag/

Summary: Fixes T4022. Hooks up the project profile controller to understanding URIs like /project/hashtag/ Also, makes handles have the new /project/hashtag/ URI by default, thus upselling that feature super duper heavily.

Test Plan: clicked some project links, noted pretty uri and page working nicely.

Reviewers: epriestley

Reviewed By: epriestley

Subscribers: chad, epriestley, Korvin

Maniphest Tasks: T4022

Differential Revision: https://secure.phabricator.com/D9260