Document API management of repositories and fix some issues with creating URIs via API
Summary:
Ref T10923. Primarily documents the process for creating repositories via the API.
Also fixes a couple of issues with repositoryPHID not being set yet when creating URIs via the API.
Test Plan:
- Followed all documented steps to create a new repository.
- Created and edited some new URIs from the web workflow, too.
Reviewers: chad
Reviewed By: chad
Maniphest Tasks: T10923
Differential Revision: https://secure.phabricator.com/D15870