Model panel diagram rendering does not work

[barnettwilliam]

The epsilon playground diagram rendering in model panels should be fixed so that models can be visualised.

[agarciadom]

For what it's worth, I've run into an odd case where the default zoom + panning of the diagram will show nothing if I have a very complex model or metamodel. I had to make the pane bigger and scroll around until I saw the actual diagram.

[szschaler]

Duplicate of #101.