"arc install-certificate", server-side components

Summary:
Provides a new workflow for making it non-horrible to install certificates.
Basically you run "arc install-certificate" and then copy/paste a short token
off a webpage and it does the ~/.arcrc edits for you.

Test Plan:
Installed certificates, used bad tokens, hit rate limiting.

Reviewed By: aran
Reviewers: aran, jungejason, tuomaspelkonen
CC: aran
Differential Revision: 460

src/aphront/default/configuration/AphrontDefaultApplicationConfiguration.php

@@ -84,10 +84,10 @@ class AphrontDefaultApplicationConfiguration
         '$' => 'PhabricatorConduitConsoleController',
         'method/(?P<method>[^/]+)$' => 'PhabricatorConduitConsoleController',
         'log/$' => 'PhabricatorConduitLogController',
+        'token/$' => 'PhabricatorConduitTokenController',
       ),
       '/api/(?P<method>[^/]+)$' => 'PhabricatorConduitAPIController',
 
-
       '/D(?P<id>\d+)' => 'DifferentialRevisionViewController',
       '/differential/' => array(
         '$' => 'DifferentialRevisionListController',