New out port function - thru group

[RadekPilich]

This function should make it possible to use some out port(s) - for example 11+12 to output the same output as the primary group out port, for example 1. To keep things simple, I would not allow additional routing and merging on these thru ports initially, just give us an easy way to set some out(s) to output the same data as on the group's primary out, while setting all the routing, remapping etc  only once on the primary out and then have MRCC automatically "channel" that out to the thru out(s), hopefully without taking as much resources as separate routing would take.