* \OC\OCSClient
* \OC\Preview
* \OC\PreviewManager
* \OC\Repair
* \OC\RepairException
* \OC\Search
* \OC\ServerContainer
* \OC\ServerNotAvailableException
* \OC\ServiceUnavailableException
* \OC\Setup
* \OC\Streamer
* \OC\SubAdmin
* \OC\SystemConfig
* \OC\TagManager
* \OC\Tags
* \OC\TempManager
* \OC\TemplateLayout
* \OC\URLGenerator
* \OC\Updater

This commit consists of patches automatically generated for this project on https://scrutinizer-ci.com

This adds a hidden config flag that allows somebody to disable the code integrity check. If `integrity.check.disabled` is set to `true` in the config file:

1. The integrity check functions will return always an empty result
2. The integrity check is not performed when installing apps
3. The integrity check is not performed when updating apps
4. The integrity check is not performed when updating the core

Furthermore this adds support for a list of channels that the code checker will run on. At the moment this is only stable because I didn't want to break any build scripts that we have. Once we have a proper CA setup and updated the build process to sign the releases we can add the RC, alpha, beta as well as daily releases. So everything except "git" basically.

This PR implements the base foundation of the code signing and integrity check. In this PR implemented is the signing and verification logic, as well as commands to sign single apps or the core repository.

Furthermore, there is a basic implementation to display problems with the code integrity on the update screen.

Code signing basically happens the following way:

- There is a ownCloud Root Certificate authority stored `resources/codesigning/root.crt` (in this PR I also ship the private key which we obviously need to change before a release 😉). This certificate is not intended to be used for signing directly and only is used to sign new certificates.
- Using the `integrity:sign-core` and `integrity:sign-app` commands developers can sign either the core release or a single app. The core release needs to be signed with a certificate that has a CN of `core`,  apps need to be signed with a certificate that either has a CN of `core` (shipped apps!)  or the AppID.
- The command ...

* resets afterwards
* adds output about the previous log level

version.php now contains the previous ownCloud version from which
upgrades are allowed. Any other upgrades will show a message that the
upgrade/downgrade is not supported.

For newer releases we shall use an integrity check. But that's a good alternative for now.

Uses the new updater url "https://updates.owncloud.com/server/"

* otherwise you don't know during which app update something failed

* add $success to the updateEnd hook
* add new return code for a update failure
* add exception class to failure hook message

* if maintenance mode was enabled before an upgrade
  it will be enabled afterwards too
* fixes #16429

* this is the preparation for some upcoming logger related changes
* also fixes an issue in the public interface where we request
  an internal class as parameter

Fixes https://github.com/owncloud/core/issues/13731