UML support

[jbaron]

Create some basic UML support, like a class diagram. Can help people to understand the project and would also provide a nice way of navigating.

Would require dealing with the AS, which right now doesn't have a stable API yet. Perhaps include a small proof of concept, but will wait with the major work until the AST access API is stable.

[jbaron]

Did some work on using SVG instead of canvas. Turned out canvas doesn't support larger dimensions and also doesn't look as good as SVG However means have to develop pretty much from scratch.