Move "Remote URI" to modern repository editor thing

Summary:
Ref T2231. Allows you to edit the remote URI and credentials.

This is a little bit funky because I'm reusing some of the pages on the new (not-yet-hooked-up) create form. Specifically, it had pages like this:

  - Repo Type
  - Name/Callsign/Remote
  - Auth
  - Done

I split "Name/Callsign/Remote" into "Name/Callsign" and "Remote", then when editing the remote I just take you through "Remote" and "Auth" and then back. This lets us reuse the giant pile of protocol/URI sanity checking logic and ends up being pretty clean, although it's a little weird that the "Create" controller does both full-create and edit-remote.

Test Plan: See screenshots.

Reviewers: btrahan, chad

Reviewed By: btrahan

CC: chad, aran

Maniphest Tasks: T2231

Differential Revision: https://secure.phabricator.com/D7405