[WebODF] using jsdom instead of xmldom

Hi all, Our tests in Node.JS do not run the DOM related tests. I looked into using JSDom instead of XmlDom. JSDom is a more complete implementation with e.g. a window object. The patch to use JSDom instead of XmlDom is attached. However, I could not run any additional tests because e.g. createTreeWalker is not implemented in JSDom. So this patch is mainly for future reference when JSDom aquires more of the DOM features that we need. https://npmjs.org/package/jsdom Cheers, Jos