* load authentication apps first

* load session apps before all other apps

correctly accross share owner and share initiator

Probably nice for the people that contributed to 9.0 to see themselves in the AUTHORS file :)

Gets rid of manual XML generation.

Fixes #13002

Move the cloud/users/{userid} code in total to the provisioning API.

This reverts commit 6a1a4880.

This changeset removes the static class `OC_Request` and moves the functions either into `IRequest` which is accessible via `\OC::$server::->getRequest()` or into a separated `TrustedDomainHelper` class for some helper methods which should not be publicly exposed.

This changes only internal methods and nothing on the public API. Some public functions in `util.php` have been deprecated though in favour of the new non-static functions.

Unfortunately some part of this code uses things like `__DIR__` and thus is not completely unit-testable. Where tests where possible they ahve been added though.

Fixes https://github.com/owncloud/core/issues/13976 which was requested in https://github.com/owncloud/core/pull/13973#issuecomment-73492969

To prevent unexpected behavior, public.php and the OCS API calls will
return 503 Service Unavailable when an upgrade is due.

We should use the proper content-type `application/xml` instead of the default `text/html` here.

Backport requested.

 /ocs/cloud/user
Response:
 <?xml version="1.0"?>
 <ocs>
  <meta>
   <status>ok</status>
   <statuscode>100</statuscode>
   <message/>
  </meta>
  <data>
   <id>thomas</id>
   <display-name>DeepDiver</display-name>
   <email>no-response@domain.tld</email>
  </data>
 </ocs>

remove the activity call here. it is not implemented anyways. This will be provided by Activity app in the future.