Utilities toolbar export model to SVG does not display custom CS images.

[harolato]

After exporting via:

The exported SVG still contains path to the image. Custom images/icons were introduced via ConcreteSyntax formalism. This makes the exported SVG to display incorrectly:

Possible solutions for a fix:

1. convert image files into base64 blobs for direct display on SVG
2. render the SVG into PNG on server/client side before download.