We already provide an interface for application developers, this file is outdated and thus should get removed.

Addresses No. 3 from https://github.com/owncloud/core/issues/14847

If the user does not exist this returns null and can lead to nasty bugs since the IDE is not indicating this...

Addresses No. 1 from https://github.com/owncloud/core/issues/14847

Doing this in the PHP code is not the right approach for multiple reasons:

1. A bug in the PHP code prevents them from being added to the response.
2. They are only added when something is served via PHP and not in other cases (that makes for example the newest IE UXSS which is not yet patched by Microsoft exploitable on ownCloud)
3. Some headers such as the Strict-Transport-Security might require custom modifications by administrators. This was not possible before and lead to buggy situations.

This pull request moves those headers out of the PHP code and adds a security check to the admin settings performed via JS.

This reverts commit 6a1a4880.

Breaking change for 8.1 wiki (Security > Administrators):

The log format for failed logins has changed and uses now the remote address and is considering reverse proxies for such scenarios when configured correctly.

This has no other reason than preventing some insane automated scanners from reporting this as security bug (which it obviously isn't as the cookie contains nothing of value)

Thus it generally results in an happier Lukas and hopefully less reports to our support and security mail addresses...

This function returns `null` when no user is logged-in.

* LDAP with multiple servers also proved backendName

As discussed at https://github.com/owncloud/core/pull/12912#issuecomment-67391155

The existing method is deprecated and just a wrapper around the manager method. Since in the future other code paths might call this function instead we need to perform that check here.

Related to http://owncloud.org/security/advisory/?id=oc-sa-2014-020

This adds a "backend" type filter to the index REST route which is a pre-requisite for https://github.com/owncloud/core/issues/12620

For example when calling `index.php/settings/users/users?offset=0&limit=10&gid=&pattern=&backend=OC_User_Database` only users within the backend `OC_User_Database` would be shown. (requires sending a CSRF token as well)

Depends upon https://github.com/owncloud/core/pull/12711

This change will expose the user backend via the REST API which is a pre-requisite for https://github.com/owncloud/core/issues/12620.

For example:
````json
[{"name":"9707A09E-CA9A-4ABE-A66A-3F632F16C409","displayname":"Document Conversion User Account","groups":[],"subadmin":[],"quota":"default","storageLocation":"\/Users\/lreschke\/Programming\/core\/data\/9707A09E-CA9A-4ABE-A66A-3F632F16C409","lastLogin":0,"backend":"OCA\\user_ldap\\USER_LDAP"},{"name":"ED86733E-745C-4E4D-90CB-278A9737DB3C","displayname":"Hacker","groups":[],"subadmin":[],"quota":"default","storageLocation":"\/Users\/lreschke\/Programming\/core\/data\/ED86733E-745C-4E4D-90CB-278A9737DB3C","lastLogin":0,"backend":"OCA\\user_ldap\\USER_LDAP"},{"name":"71CDF45B-E125-450D-983C-D9192F36EC88","displayname":"admin","groups":[],"subadmin":[],"quota":"default","storageLocation":"\/Users\/lreschke\/Programming\/core\/data\/71CDF45B-E125-450D-983C-D9192F36EC88","lastLogin":0,"backend":"OCA\\user_ldap\\USER_LDAP"},{"name":"admin","displayname":"admin","groups":["admin"],"subadmin":[],"quota":"default","storageLocation":"\/Users\/lreschke\/Programming\/core\/data\/admin","lastLogin":"1418057287","backend":"OC_User_Database"},{"name":"test","displayname":"test","groups":[],"subadmin":[],"quota":"default","storageLocation":"\/Users\/lreschke\/Programming\/core\/data\/test","lastLogin":0,"backend":"OC_User_Database"}]
```

* files_encryption
* files_versions
* files_trashbin
* tests
* status.php
* core
* server container

First step of a somewhat testable user management. - I know, the JSON returns are in an ugly format but the JS expects it that way. So let's keep it that way until we have time to fix the JS in the future.

Check already implemented in core/settings/ajax/changedisplayname.php

This will use the new Hashing API for OC_User_Database and migrate old passwords upon initial login of the user.