This gives a clean break between the transfer request and the type of
transport allocated to make way for transports that need to switch
types (to support driving to a port, then getting on a ship, to a train,
then back on the road, etc).
https://github.com/Khopa/dcs_liberation/issues/823
Downside to the current implementation is that whether or not transports
that were purchased last turn will be available for airlift this turn is
arbitrary. This is because transfers are created at the same time as
units are delivered, and units are delivered in an arbitrary order per
CP. If the helicopters are delivered before the ground units they'll
have access to the transports, otherwise they'll be refunded. This will
be fixed later when I rework the transfer requests to not require
immediate fulfillment.
https://github.com/Khopa/dcs_liberation/issues/825
Historically this inherited from Event but there was no reason for that.
That's gone now. Finish the separation and move the unit order tracking
class out of the combat results reaction class's file.
