Signed-off-by: Joas Schilling <coding@schilljs.com>

* Move routes to app
* Move routes over to the AppFramework
* Fix tests

There is plenty of stuff to fix properly here. But out of scope for now.

* 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.