SotBE S18: some changes to map

Make Shan Taum’s keep larger and the path to it easier.  Both of those
changes make the scenario a little harder.
SotBE S18: make all guards loyal
SotBE S18: make the human enemy AI leader passive

… so that one cannot make him leave his keep suicidally.
SotBE S18: decrease human enemy AI aggression during nighttime
SotBE S18: increase aggression of orc enemy AI
SotBE S18: make human ally AI protect its leader (Howgarth)

Since Howgarth may not die, this takes some randomness out of the
scenario.
SotBE S18: minor tweak to starting villages for side 6
SotBE S18: minor change to starting location of human reinforcements
SotBE S18: balancing adjustments to gold and income