Set reasonable defaults when displaying remote repository URIs.

Summary: Show SSH user on git-over-ssh repositories and hide both username and password for other repos.

Test Plan: View repository details page in diffusion, Clone URI should appear with a username (taken from repo config) and any http(s) repos should be without usernames.

Reviewers: epriestley, #blessed_reviewers

Reviewed By: epriestley

CC: Korvin, epriestley, aran

Maniphest Tasks: T4147

Differential Revision: https://secure.phabricator.com/D7631