Enhancement: webdav support in web-client package

Only relevant for developers:
We've added webdav support to the `web-client` package. This wraps the existing webdav requests from ownCloud SDK but
handles the differentiation of public link and user-specific webdav requests internally.

https://github.com/owncloud/web/pull/7430
https://github.com/owncloud/web/pull/7880