Ensure we don’t drop data when someone subscribes too late

[hoichi]

Not sure we want to block execution and make subscribing to every output channel obligatory, but there’s a nagging suspicion we could lose shit if someone subscribes too late.

Possible solutions:

• Do make subscribing to every output channel obligatory (not so hot idea for 'template' channel on Renderer).
• Buffer the unclaimed baggage. Will consume memory, should be destroyed when freeing resources ($ToDo)
• ?