* Add a Ref option to SearchRequest, e.g. for limiting the search to a space
* Enable REPORT requests for /dav/spaces URLs
* Limit the search to the according space in case of /dav/spaces searches
* Add changelog
* Adapt expected failures
* Comment exported functions
This avoids using a public global variable. It allows us to initialize
the default client a bit later (outside of init()). That way we can e.g.
properly initialize the in-memory registry.
