added webdav, node, package.json, refs #13

Using [jsdav](https://github.com/mikedeboer/jsDAV) I implemented a basic webdav server functionality.

For simplicity I introduced vhosts managed by an express server. You can just `sudo node couchrp.js` (as root because the vhosts server runs on port 80 by now) and use `webdav.localhost` (or `webdav.yourdoma.in` if you want) as webdav folder.