Replace /conpherence/N/ with /conpherence/view/N/.

Summary:

• Move /N/ to /thread/N/.
• Move /view/N/ to /N/.
• This makes the mobile "Conpherence -> click thread -> see thread" workflow work correctly. This also makes permalinks work correctly on mobile.

Ref T2421.

Test Plan: Clicked flows on desktop, mobile.

Reviewers: btrahan

Reviewed By: btrahan

CC: aran

Maniphest Tasks: T2421

Differential Revision: https://secure.phabricator.com/D5508