Provide event handler name from event super class
Remove module names from event handler names
Add started state for components

This change adds a started states to compnents, so that when step is
invoked the first time, the on_start handler is invoked (without popping
events from inbox). After the initial step invokation, events are popped
from the inbox as usually.
Add event handler tests for events in modules
Add initial worker

Initial version of a worker, meant to be stepping components non stop in
executions.