...as https-equivalent to complement vnd.sun.star.webdav scheme.  See the mail
thread starting at
<http://lists.freedesktop.org/archives/libreoffice/2015-August/069929.html>
"What autogen.sh for an alternative ContentProvider for dav:// scheme?" for why
it is considered beneficial to have the WebDAV UCP support---in addition to the
standard pair of http[s] schemes---a non-standard pair of
vnd.sun.star.webdav[s] schemes different from the "accidentally supported"
non-standard pair of dav[s].

Change-Id: I7032aa1ed599f735969cf0163cd9dc121a1fdcb3