add mkcol and delete interface to webdav backend, move webdav vfs logic to operation webdav

add minimal mkcol implementation and prepare delete webdav

add proppatch handler to default backend webdav

implement webdav_proppatch webdav

add proppatch op webdav

add proppatch interface webdav

make multistatus response ready for proppatch requests webdav

(0) -100 -30 -10 -7 +7 +10 +30 +100 tip

mercurial