Quick replace train station modules.

Allow replacement of station modules quickly in the same way as upgrading buildings.
Simply place the new module on top of an existing to swap them without needing to deconstruct an existing one to rebuild a new one. Doing this without altering the tracks would also allow it to be done without interrupting train traffic through the station.

We alread can do that (just hold shift which works for storages too) - exception is empty statin module, which currently cannot be quick replaced, i presume that lower cost may be the problem. It would be nice we could replace that too.