Arbitrary webdav URL support

[JammingBen]

Currently, methods like getFileContents always goes to a path like {{host}}/remote.php/webdav/..., e.g. https://localhost:9200/remote.php/webdav/12345. Spaces require to query URLs like https://localhost:9200/dav/spaces/12345, hence we need to support arbitrary webdav URLs.