Reading EntityReference on open when use as a node

Read EntityReference node and add it to the SvgDocument.

```
<?xml version="1.0"?>
<svg xmlns="http://www.w3.org/2000/svg" width="800px" height="800px">
  <g>
    <rect width="200px" height="200px" fill="black" />
    <text x="100px" y="100px" font-family="Verdana" font-size="24" fill="white" text-anchor="middle">&name;</text>
  </g>
</svg>
```
Merge pull request #73 from Guymestef/master

Reading EntityReference on open when use as a node