R1:5f6ea9f662aa

Activate the new Repository creation workflow

Summary:
Ref T2231. This:

- Activates the new multi-step workflow, and exposes it in the UI.
- Adds "can create", "default view" and "default edit" capabilities.
- Provides a default value for `repository.default-local-path` and forces repositories into it by default. It's still editable, but Phabricator gets it correct (for some definition of correct) by default now.

Test Plan: Created some new repositories with the new workflow.

Reviewers: btrahan…