Give users a modal VCS choice when creating a new repository

Summary:
Ref T10748. Allow the new EditEngine workflow to create repositories by giving the user a modal repository type choice upfront.

(The rest of this flow is still confusing/weird, though.)

Test Plan:
  - Created a new repository.

{F1249626}

Reviewers: chad

Reviewed By: chad

Maniphest Tasks: T10748

Differential Revision: https://secure.phabricator.com/D15813

src/applications/diffusion/management/DiffusionRepositoryURIsManagementPanel.php

@@ -106,7 +106,7 @@ final class DiffusionRepositoryURIsManagementPanel
         ));
 
     $doc_href = PhabricatorEnv::getDoclink(
-      'Diffusion User Guide: Repository URIs');
+      'Diffusion User Guide: URIs');
 
     $header = id(new PHUIHeaderView())
       ->setHeader(pht('Repository URIs'))