- Improved exploration algorithm. AI will avoid dead-end barriers and thus explore much faster.

- Fixed crash when there are no heroes available to recruit in the map. TODO: make AI handle it
- Fixed crash when Chain Lightning has not enough targets
- Fixed crash at Hill Fort (?)
- AI will buy Spellbook for its heroes
- AI will try to use Cartographer and Observatory when exploring
- AI will not visit Prison when heroes are at max
- Experiment: AI will try to capture Mines and Dwellings when there are no enemies around (part of CONQUER goal)

lib/CBattleCallback.cpp

@@ -1940,6 +1940,8 @@ std::set<const CStack*> CBattleInfoCallback::getAffectedCreatures(const CSpell *
 			{
 				possibleHexes.erase (hex); //can't hit same place twice
 			}
+			if (!possibleHexes.size()) //not enough targets
+				break;
 			lightningHex = BattleHex::getClosestTile (attackerOwner, destinationTile, possibleHexes);
 		}
 	}