Fixes https://github.com/owncloud/core/issues/13326

This reverts commit 6a1a4880.

Reasoning:
- a WebDAV server is not required to implement locking support
- WebDAV Locking is know to break the sync algorithm
- the current lock implementation is known to be broken (locks are not moved if a file is moved, locks on shared files don't work)

- VObject fixes for Sabre\VObject 3.3
- Remove VObject property workarounds
- Added prefetching for tags in sabre tags plugin
- Moved oc_properties logic to separate PropertyStorage backend (WIP)
- Fixed Sabre connector namespaces
- Improved files plugin to handle props on-demand
- Moved allowed props from server class to files plugin
- Fixed tags caching for files that are known to have no tags
  (less queries)
- Added/fixed unit tests for Sabre FilesPlugin, TagsPlugin
- Replace OC\Connector\Sabre\Request with direct call to
  httpRequest->setUrl()
- Fix exception detection in DAV client when using Sabre\DAV\Client
- Added setETag() on Node instead of using the static FileSystem
- Also preload tags/props when depth is infinity

This checks if the offset exists before accessing it and also adds unit tests to this function which would have catched this before 

Fixes https://github.com/owncloud/core/issues/14277

This enforces proper types on POST and GET arguments where I considered it sensible. I didn't update some as I don't know what kind of values they would support 

Fixes https://github.com/owncloud/core/issues/14196 for core

Some code paths called the `normalizePath` functionality with types other than a string which resulted in unexpected behaviour.

Thus the function is now manually casting the type to a string and I corrected the usage in list.php as well.

This file is unused and has been last modified two years ago. Furthermore it won't evne work anymore properly because it uses things  like `CONFIG_DATEFORMAT` which are gone a long time ago...