Extend observable behavior and/or reconsider the behavior

[PGijsbers]

The current subject-observer pattern only supports evaluations (here).
However, I think instead of directly adding the interface to the GAMA object, there could be a completely isolated object which just parses the GAMA log and performs callbacks.

The advantage is more isolation. However this means that objects passed along from these events are no longer the same objects as are being handled in the evolutionary algorithm, but rather parsed interpretations.
Also, I don't know if it is good/bad practice to create use the logging module for this isolation.

Either way, more events should be exposed, e.g. mutation, selection and elimination. As such, it might also be more sensible to link it to the operator set.