switch pfilamp accounting to match dcb scheme

The pfilamps declare the lamp states when turning them on and off. This can only work for header cards if the exposure headers are constructed at just the right time.

The dcbs have switched to a much better scheme, where the actor broadcasts the last on and off times for each lamp. If the actor waits until the integration is done it will get the right values, and you get nice windowing calculations with shutters, etc.

Pretty straightforward to add.