Added oc:tags and oc:favorites in PROPFIND response.
It is possible to update them with PROPPATCH.
These properties are optional which means they need to be requested
explicitly
Whenenver range headers are set and encryption is enabled, it is not
possible to automatically fseek() to the proper position.
To avoid returning corrupt/invalid data or causing a decryption error,
the range headers are stripped so that the SabreDAV code in httpGet()
returns the whole file.
