Move the repository policy step into the create workflow

Summary:
Fixes T4242. It's currently possible to set nonsense defaults and create repositories with unintended policies, because policy configuration isn't part of creation. Instead:
  - put a policy page into the creation workflow;
  - require the selection of valid policies (i.e., prevent creating a repository you can't view / edit).

Test Plan:
  - Created imported and hosted repositories, hit policy selection.
  - Edited policies of existing repositories.
  - Tried to set nonsense policies.

Reviewers: btrahan

Reviewed By: btrahan

CC: aran

Maniphest Tasks: T4242

Differential Revision: https://secure.phabricator.com/D7856

src/applications/diffusion/application/PhabricatorApplicationDiffusion.php

@@ -73,11 +73,11 @@ final class PhabricatorApplicationDiffusion extends PhabricatorApplication {
             'encoding/' => 'DiffusionRepositoryEditEncodingController',
             'activate/' => 'DiffusionRepositoryEditActivateController',
             'dangerous/' => 'DiffusionRepositoryEditDangerousController',
-            'policy/' => 'DiffusionRepositoryEditPolicyController',
             'branches/' => 'DiffusionRepositoryEditBranchesController',
             'subversion/' => 'DiffusionRepositoryEditSubversionController',
             'actions/' => 'DiffusionRepositoryEditActionsController',
             '(?P<edit>remote)/' => 'DiffusionRepositoryCreateController',
+            '(?P<edit>policy)/' => 'DiffusionRepositoryCreateController',
             'local/' => 'DiffusionRepositoryEditLocalController',
             'delete/' => 'DiffusionRepositoryEditDeleteController',
             'hosting/' => 'DiffusionRepositoryEditHostingController',