get sound by depth
add ambient sound effects to battlescape

defined by terrain type.
merge + draw Craft in the baseScape using an order that makes sense.

- BaseView

also on previous commit,
	TileEngine: use a bell curve for damageTypes (but not DT_IN ...)
	ConfirmLoadState: surface adj.

Merge branch 'master' of https://github.com/SupSuper/OpenXcom into oXc_kL
Conflicts:
	src/Battlescape/BattlescapeGame.cpp
	src/Battlescape/BattlescapeGame.h
	src/Battlescape/BattlescapeGenerator.cpp
	src/Battlescape/BattlescapeState.cpp
	src/Battlescape/ExplosionBState.cpp
	src/Battlescape/Inventory.cpp
	src/Battlescape/Inventory.h
	src/Battlescape/InventoryState.cpp
	src/Battlescape/ProjectileFlyBState.cpp
	src/Battlescape/UnitDieBState.cpp
	src/Battlescape/UnitTurnBState.cpp
	src/Battlescape/UnitWalkBState.cpp
	src/Engine/Game.cpp
	src/Engine/Sound.h
	src/Resource/ResourcePack.h
	src/Ruleset/RuleTerrain.cpp
	src/Ruleset/RuleTerrain.h
	src/Savegame/SavedBattleGame.cpp
	src/Savegame/SavedBattleGame.h