Clean up display of clone URIs a little bit

Summary:
Ref T10923. This makes the "Clone URI" UI a little nicer:

• Show whether each URI is read-only, read-write, or external.
• Clicking the button selects the URI.
• Add a link to manage the appropriate credentials.

Test Plan:

Reviewers: chad

Reviewed By: chad

Maniphest Tasks: T10923

Differential Revision: https://secure.phabricator.com/D15891