Added tests for DAV_Status
Added tests for DAVACL_Element_ace
Fixed DAV_Resource tests to use assertSame instead of assertEquals
Removed the seemingly redundant DAVACL_Element_href

DAVACL_Element_href is almost identical to DAV_Element_href, except for a
filter for double hrefs in the toString() method of the latter. As I didn't see
DAVACL_Element_href being used anywhere, I just removed it.
Added tests for DAVACL_Element_supported_privilege