Make movement aware of tile owners #799
Description
Right now movement cost calculations here do not take into account whether or not the tile is within a civ's borders. That can be found via this variable in the tile class. Civ A's units shouldn't be able to use Civ B's roads without a right of passage.
Possible bonus work, implement right of passage agreements (though this is a big enough change that it probably warrants a separate issue, as we don't yet have multi-turn trade deals implemented)