[Add-on] possibilty to notify other add-ons about model / RTD changes

[dvojtise]

Some add-on may change the runtime data during the execution.
For example using the timeline, the trace add-on may reset the RTD to a previous state.
Some UI add-on may directly apply user input to the running model.

It would be useful that this change is notified to the other add-ons, so they can take it into account.

A typical use case would be: add-ons that display a view of the RTD would be able to refresh their view when the user navigates in the trace.

I propose to add a new callback method in IEngineAddon for this.

Ideally, it should also contain some information about the reason of the change.
Some reasons I can list now:

• trace navigation (the change is temporary/reversible)
• user data input (i.e. the user directly set a data in the model using the add-on UI) (the change is permanent and will not be reverted)