Improvements:

- Fixed Layers issues.
- Changed Explosion treshold for breaking.
- Added 2 types of platform breaking sound.
- Examinating broken platform give now feedback that its destroyed in description.
- Separated "Indestructable" and "Broken" to give two different feedbacks depending on platform status.

code/game/objects/structures/platforms.dm

@@ -67,11 +67,11 @@
 			if (prob(15))
 				broken()
 				return
-		if(EXPLOSION_THRESHOLD_LOW to EXPLOSION_THRESHOLD_MEDIUM)
+		if(EXPLOSION_THRESHOLD_LOW to EXPLOSION_THRESHOLD_HIGH)
 			if (prob(35))
 				broken()
 				return
-		if(EXPLOSION_THRESHOLD_MEDIUM to INFINITY)
+		if(EXPLOSION_THRESHOLD_HIGH to INFINITY)
 			broken()
 			return
 	return