Loading/exporting models in AEON format

[ondrej33]

We should be able to load models in AEON format and perhaps also extend the format (in a standardized way) to accommodate new components of the sketch. It already supports the model annotations, which could be used to represent most of the sketch parts that are not supported directly.

I see several "steps":

• [x] Loading models in plain AEON format. This is super useful for testing purposes at the moment.
• [x] Loading models in AEON format with model annotations that would include HCTL formulas for dynamic properties and FO formulas for static properties. It is also helpful for testing inference workflows but not pressing.
• [x] Design how to standardize the annotations for other kinds of template properties and extend the loader to cover these two.

I think the first two are critical and should be relatively straightforward to implement. The last one is not really critical at the moment, but it would be a nice addition before a proper release.

We should also make it possible to export the models in (extended) AEON format, covering as much of the sketch as possible.

Lastly, SBML support would be practical too. This will be easier to implement once we have a format for representing all the template properties.

[ondrej33]

With #47 and #48, the first two tasks are finished. We still need to finish task 3. That is, extend/standardize the AEON format to cover template properties and datasets.

[ondrej33]

This is now mostly done with #57. Other entities are encoded with JSON annotations. We might get back to this in future and make the format rely more on the annotation system itself, instead of encoding the entities with JSON.