Disables the 'create transfer order' button in the unit transfer dialog if no units are actually selected for transfer (including when the dialog is first loaded).
The simple form of this works, but without the multi-mode routing it'll
only get used when the final destination is a port with a link to a port
with a factory.
These also aren't targetable or simulated yet.
https://github.com/Khopa/dcs_liberation/issues/826
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
UI isn't finished. Bulk transfers where the player doesn't care what
aircraft get used work (though they're chosen with no thought at all),
but being able to plan your own airlift flight isn't here yet.
Cargo planes are not implemented yet.
No way to view the cargo of a flight (will come with the cargo flight
planning UI).
The airlift flight/package creation should probably be moved out of the
UI and into the game code.
AI doesn't use these yet.
https://github.com/Khopa/dcs_liberation/issues/825
This adds the models and UIs for creating ground unit transfer orders.
Most of the feature is still missing:
* The AI doesn't do them.
* Transfers can move across the whole map in one turn.
* Transfers between disconnected bases are allowed.
* Transfers are not modeled in the simulation, so they can't be
interdicted.
https://github.com/Khopa/dcs_liberation/issues/824
