URI: change backslashes in name to forward slashes

For compatibility with systems that denote URI's in the Windows format:
\\server\share\path\to\file

An example of an URI encountered in this format is the 'sambaHomePath' entry in
LDAP.
Strip workgroup from username, for backwards compatibility

See also issue #3: stripping off the domain should be configurable. We will
introduce this in a future version, but for now, keep the old behaviour.
server.php: probably harmless compat fix for Word 2003

Word 2003 will not write to a file unless this flag is set to true; else
something goes wrong during the locking process. Setting this flag is probably
harmless according to http://sabre.io/dav/clients/msoffice.