Rename world to model

[DavidKerkmann]

Motivation / Current Behaviour

As a subset of #400 we should rename the world to model to use identical names and patterns.

Enhancement description

Renaming is done quickly. One should do the passing to the Simulation similar to the ODE models and think about templates for the world/model.

Additional context

No response

Checklist

• [X] Attached labels, especially loc:: or model:: labels.
• [X] Linked to project

[mknaranja]

The abm.h could/should probably be removed and replaced by model.h then.