Remove @internal from DcaReadingDataDefinitionBuilder::getFromDca().
Deprecate the EventPropagator.

We simply realized that propagation is not the way to go as it creates
more problems than it solves.

In final DCG 2.0.0 it will be completely removed and therefore you
should switch to plain event handling.
Remove the event propagator and replace with plain event dispatching.

For the moment the old propagation pattern is simulated but will be
removed in future.