While working on #1350 I realized that using dt for actions during initialization is risky, because it is not really clear what dt means at thsi point in time. Under certain circumstances dt is not even known (if second participant performs a write actions during initialize and it has not yet received the dt from the first participant).

I'm labelling this as a bug, because I think this is currently a generally design issue.

I see two options:

• don't perform any actions during initialize
• remove actions that rely on dt

Sightly related: #1352. This might fix the issue that for the second participant in serial coupling initialize is actually a merge of initialization and receiving results from the first window of the first participant. I've split these two steps up here. So we can also perform no action in the first half and perform all the usual actions in the second half.