By separating them from unrelated code, their dependents
can use them without depending on unrelated code, which
in turn helps to reduce cyclic dependencies.
When flying in shared cockpit mode, both pilots log into the network.
One as pilot to be visible to ATC and other pilots. The other one as
observer. For the observing user, the pilots aircraft needs to be filtered.
Filter algorithm is using the same schema as vPilot does.
ref T427
This is an intermediate step to have smaller unit tests. It is a trade off
between having many many test executables compared to a few bigger ones. But
this comes a lot closer to what QtTest is meant to be used.
