SVG Command line tool for exporting output

It will be faster it you finish DOMElement function here, and define methods below as prototype of DOMElement, e.g.

```
DOMElement.prototype = {
  setAttributeNS: function DOMElement_setAttributeNS(NS, name, value) {
    ...
  },
  appendChild: function DOMElement_appendChild(element) {
    ...
```