Allow OAuth applications to be disabled instead of destroyed

Summary: Ref T7303. This interaction is very oldschool; modernize it to enable/disable instead of "nuke from orbit".

Test Plan:
  - Enabled applications.
  - Disabled applications.
  - Viewed applications in list view.
  - Generated new tokens.
  - Tried to use a token from a disabled application (got rebuffed).
  - Tried to use a token from an enabled application (worked fine).

Reviewers: chad

Reviewed By: chad

Maniphest Tasks: T7303

Differential Revision: https://secure.phabricator.com/D15620

resources/sql/autopatches/20160405.oauth.2.disable.sql

@@ -0,0 +1,2 @@
+ALTER TABLE {$NAMESPACE}_oauth_server.oauth_server_oauthserverclient
+  ADD isDisabled BOOL NOT NULL;