[Trace] possibility to record only some runtime data

[dvojtise]

In some models, some runtime data are actually constant during the execution.

This is the case for some constants that are evaluated during the model initialization, then will never change.
It is then useless to store them (speed and memory impact) and to congest the UI.

It would be useful to be able to indicate to the trace add-on which data dimensions should be handled either by not considering some data dimensions at all or by dealing with them differently in the trace model.

In more advanced scenario implying #158 (pause/resume add-on) we can also think about changing considered data dimensions