document.evaluate / XPath not supported in any IE version

Looks like we might need to a different approach for parsing the XML to be cross-browser compatible.

For now, ownCloud uses a different but less accurate implementation (it assumes that the prefix is always "d:") but works for our use case: https://github.com/owncloud/core/blob/jsocclient/core/js/files/ie8davclient.js#L116

Ideal would be to fine-tune that approach to be more accurate.
