more naming convention

now there are spawn objects!
now entity spawns are loaded from level!
now entity spawns are saved to level!

code/entities/arrow.lua

@@ -1,10 +1,10 @@
 Arrow = Entity:new()
+Arrow.type = "Arrow"
+
 
 function Arrow:new(x,y,rotation,speed)
 	local o = Entity:new(x,y)
 
-	o.type = "arrow"
-
 	o.pos = {x = x, y = y}
 	o.speed = speed or 10
 	o.sprite_rotation = rotation or 0