Use OpaqueEnvelopes for all passwords in Phabricator

Summary:
See D2991 / T1526. Two major changes here:

  - PHP just straight-up logs passwords on ldap_bind() failures. Suppress that with "@" and keep them out of DarkConsole by enabling discard mode.
  - Use PhutilOpaqueEnvelope whenever we send a password into a call stack.

Test Plan:
  - Created a new account.
  - Reset password.
  - Changed password.
  - Logged in with valid password.
  - Tried to login with bad password.
  - Changed password via accountadmin.
  - Hit various LDAP errors and made sure nothing appears in the logs.

Reviewers: vrana, btrahan

Reviewed By: vrana

CC: aran

Differential Revision: https://secure.phabricator.com/D2993

src/applications/auth/controller/PhabricatorLDAPLoginController.php

@@ -37,9 +37,8 @@ final class PhabricatorLDAPLoginController extends PhabricatorAuthController {
 
     if ($request->isFormPost()) {
       try {
-        $this->provider->auth($request->getStr('username'),
-          $request->getStr('password'));
-
+        $envelope = new PhutilOpaqueEnvelope($request->getStr('password'));
+        $this->provider->auth($request->getStr('username'), $envelope);
       } catch (Exception $e) {
         $errors[] = $e->getMessage();
       }