Unfortunate choice of graph source format

[d-stahl-ericsson]

Description

All graph sources in the repository are currently on Gliffy format. Gliffy is just one tool, and not very actively maintained at that (at least not the desktop version, which has compatibility issues with the web version).

SVG format would be preferable.

Motivation

Avoid tool lock-in.

Exemplification

The usage-examples images would be affected.

Benefits

Having all graphs in SVG format instead of Gliffy's private format would allow changes to be made using any tool.

Possible Drawbacks

It is possible that the Gliffy format allows features not supported by SVG. I have not found that the existing images have any such issues.