Parsing documents from inkscape

When I am loading an document from inkscape, I always get an error. Loader is not able to load unknown elements.

I did two commits:
1) SvgElementFactory.cs: I added check of the namespace (dc:title was loaded as SvgTitle)
2) SvgDocument.cs: Unknown elements are added to stack too.

```xml
<?xml version="1.0" encoding="UTF-8" standalone="no"?>
<!-- Created with Inkscape (http://www.inkscape.org/) -->
<svg xmlns:dc="http://purl.org/dc/elements/1.1/" xmlns:cc="http://creativecommons.org/ns#" xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#" xmlns:svg="http://www.w3.org/2000/svg" xmlns="http://www.w3.org/2000/svg" xmlns:sodipodi="http://sodipodi.sourceforge.net/DTD/sodipodi-0.dtd" xmlns:inkscape="http://www.inkscape.org/namespaces/inkscape" width="54" height="54" id="svg4135" version="1.1" inkscape:version="0.48.4 r9939" sodipodi:docname="indicator.svg" transform="matrix(4.5,0,0,4.5,0,0)">
  <rect style="background: #000000;" width="12" height="12" />
  <g>
    <defs id="defs4137" />
    <sodipodi:namedview id="base" pagecolor="#ffffff" bordercolor="#666666" borderopacity="1.0" inkscape:pageopacity="0.0" inkscape:pageshadow="2" inkscape:zoom="22.4" inkscape:cx="-15.375" inkscape:cy="5.0598572" inkscape:document-units="px" inkscape:current-layer="layer1" showgrid="true" inkscape:window-width="1920" inkscape:window-height="1174" inkscape:window-x="1276" inkscape:window-y="-4" inkscape:window-maximized="1">
    <inkscape:grid type="xygrid" id="grid4143" empspacing="3" visible="true" enabled="true" snapvisiblegridlinesonly="true" />
    </sodipodi:namedview>
    <metadata id="metadata4140">
      <rdf:RDF>
        <cc:Work rdf:about="">
          <dc:format>image/svg+xml</dc:format>
          <dc:type rdf:resource="http://purl.org/dc/dcmitype/StillImage" />
          <dc:title />
        </cc:Work>
      </rdf:RDF>
    </metadata>
    <g inkscape:label="error" inkscape:groupmode="layer" id="layer1" transform="translate(0,-1040.3622)" style="" fill="#BFBFBF">
      <path style="stroke:none" d="M 1,1 1,11 11,11 11,9 3,9 3,7 6,7 6,5 3,5 3,3 11,3 11,1 z" id="path3761" inkscape:connector-curvature="0" transform="translate(0,1040.3622)" />
    </g>
  </g>
</svg>
```