Add repository URI view pages and IO/Display edit logic

Summary:
Ref T10748.

• New View page for repository URIs.
• Make display and I/O behavior (observe, mirror, read, read/write) editable.
• Add a bunch of checks to prevent you from completely screwing up a repository by making it writable from a bunch of differnet sources.

Test Plan:

Reviewers: chad

Reviewed By: chad

Maniphest Tasks: T10748

Differential Revision: https://secure.phabricator.com/D15816