The EventReceiverLike interface provides base event routing and handling for all the event receivers
that are injected into an EventSource.
All base methods are no-ops, implementers can chose to implement only those they need, and compose freely
from other traits. Note, the onPreprocEvent, onOnEvent and onUnEvent handlers are called for each inbound
preproc, on and un event before routing to the typed event handler for each, resulting in at least two
handler calls for each event type.