SotBE S15: add some road hexes to western part of map

This has negligible effect on the fighting, but means that Kapou'e
doesn't have to spend many turns drudging through difficult terrain to
get to the signpost at the end of the scenario (if he was involved in
the fighting).
SotBE S5: make one of the AI leaders a Death Knight

This is mostly just for variety, but gives the player the option to use
different units types more effectively against one leader than the
other.