Run cleanup of expired DB file locks to background job

Properly check path validity before deleting to trash

* fixes #22819

The old way fired a DELETE statement on each destruction of the
DBLockingProvider. Which could cause a lot of queries. It's enough
to run this every 5 minutes in a background job, which in the end
could result in file locks that exists 5 minutes longer - in the
worst case and for not properly released locks.

This makes the DB based locking a lot more performant and could
result in a similar performance to the Redis based locking provider.

Add release channel selection back

allow availability recheck for external storages

This prevents deleting the whole "files" folder of the user whenever
$ownerPath is empty. This can happen in concurrency situations.

Allows to select the release channels again and also shows the last check date

ucwords does not support delimiter before 5.4.32

Rename and move permissions are set when a file is updatable

Fix download spinner to work with CSS styles

A recent change replaced img elements with CSS icons for file actions.
This fix adjusts the logic to work properly with CSS icons instead of
images.

* Fix unit tests

Keep "encryptedVersion" when calling `\OC\Files\View::copy`

Exclude the assets folder from integrity check

When calling `\OC\Files\View::copy` we should also keep the version to ensure that the file will always have the correct version attached and can be successfully decrypted.

To test this the following steps are necessary (from https://github.com/owncloud/core/issues/22781#issuecomment-191328982):

1. setup a new ownCloud 9.0 beta2
2. enable encryption
2. upload a docx (5.7MB large)
3. upload the same file again and overwrite the existing file
4. I can download the original file and the first version
5. I restore the first version
6. restored version can no longer be downloaded with the error described above

The manual cache operation in `\OCA\Files_Versions\Storage` is unfortunately necessary since `\OCA\Files_Versions\Storage::copyFileContents` is not using `\OCP\Files\Storage::moveFromStorage` in the case when an object storage is used. Due to the workaround added in https://github.com/owncloud/core/commit/54cea05271b887f1c8062c034741df869bc0f055 the stream is directly copied and thus bypassing the FS.

We should not scan the assets folder as this can contain user specific content. Partially addresses https://github.com/owncloud/core/issues/22803

untangle different user manager instances, fixes #22770

Remove browser autocomplete in new file menu

Minor grammar in config.sample.php

Fix this here in the source so it will propogate into the documentation.
Edit was already applied in https://github.com/owncloud/documentation/pull/2208 but needs to be done here at the source.

Translate strings of federation admin section

Add Versions app header to config.sample.php

Master is now 9.1

Update copyright information and author file

Exclude custom data directory from integrity checker

allow putting the part file in the view root