extract has_position trait

src/game.rs

@@ -1,7 +1,7 @@
 use crate::level::{Level, StructureElement};
 use crate::level_generator::LevelGenerator;
 use crate::player::Player;
-use crate::position::Position;
+use crate::position::{HasPosition, Position};
 
 pub const LEVELS: usize = 10;