Added DAV client wrapper that support timeout values

Since SabreDAV does not support passing a timeout value to curl, this
commit adds a subclass for it that will set the timeout value to
curlRequest().
Added timeout value to WebDAV post setup check

Fixes #5357
Fixed spaces
Merge pull request #5358 from owncloud/postinstall-ocdavclientwithtimeout

Added timeout for WebDAV post setup check