Investigate connections between streams/maps and triggers

[jm9e]

There might occur problems when a trigger is listening on a map or a stream if only sub or subs is connected. In this case the trigger will never fire.

Possible solution

1. Map
   When connecting a map with a trigger you could either ask the user to connect with a map sub port instead or arbitrarily descend and do it automatically.

2. Stream
   This one is more difficult. One solution would be to remember the source port and descend. When pulling from this port, it would suffice if an appropriate marker (ideally BOS) appears.