Implement walls on Jebel Barkal, beautify the map, improve the trigger script and...

Implement walls on Jebel Barkal, beautify the map, improve the trigger script and add stables/cavalry attckers, refs #5040.
Display "Napata will attack in %(time)s!" to observers, string addition permitted by Itms.

Mapgen:
Use the EntitiesObstructionPlacer from rP21555, the wall constraints and return values from rP21554,
so that there are no walls at the hill and to keep gates free.
Add palms to the city blocks and guardians at the central path.
Carve out temple areas using the EntitiesObstructionPlacer, rather than having half the temple submerged by the mountain.
More treasures on the hill and in the city and allow mines on top of the hill.

Triggerscript:
Make units always patrol, since the attack-walk order runs out and then units accumulated after eradicating a player.
This also fixes the inconsistency that units captured after that order ran out, but not before.
Don't use the violent stance since this also allows capturing.
Move attacker targetClasses to attacker balancing composition object, so that it can be fine-tuned for every attackergroup.

Balancing:
Place Stables which only spawns melee cavalry which only attack traders, women and siege engines.
Nerf fortresses by not exclusively spawning champions (temples still do).

git-svn-id: https://svn.wildfiregames.com/public/ps/trunk@21556 3db68df2-c116-0410-a063-a993310a9797