Change to via convoy dialogue

The new WitA code also contains a small change on via convoy. Following a suggestion, the via convoy dialogue box (the one that asks if you want to use a land or convoy route where both exist) will only come up if the fleet(s) adjacent to the army being order to move all belong to other countries. So in other words, if you order A Brest - Gascony and you have a fleet in MAO, there will be no box. If the fleet in MAO belongs to another country, you will be asked to specify land or convoy route.