Added first version of the event ontology and the viewer UI.

Added first version of the event ontology and the viewer UI.
* Event plug-ins can be found in the simantics-incubator repository at /event/trunk.
* Ripped experiment run handling out of ExperimentManager to simplify it and leave run handling up to IModel implementations. Fixed too early experiment activation problems in Apros - now experiment activation callback is invoked only when activation is completely done.
* All experiment runs are marked as event producers in the model during experiment activation. This will bring their data into the event view.
* Added a very simple AprosEventWriter that produces events into experiment run instances by listening to Apros through AprosListener. This needs much more work.

TODO:
* Add a selection processor for the selection view of the event view. Make it contribute tab by adapting the input into a ComparableTabContributor.
* Make event producers and events adaptable to property tab contributors.

refs #2136

git-svn-id: https://www.simantics.org/svn/simantics/sysdyn/trunk@19458 ac1ea38d-2e2b-0410-8846-a27921b304fc