Rules are not template anymore (it was dumb)

Entities are now managed with unique_ptr to allow polymorphism (and good memory management)
Rules can be added via the Level object
Fixed Rule::findTarget not caring about targetType

TODO : Find why pathfinding (unlikely) or findTarget (most likely) is broken

src/Entity.h

@@ -51,6 +51,7 @@ public:
     virtual void update();
 
     virtual State getState() const;
+    virtual EntityType getType() const;
     virtual pro_maat::GridPos getTarget() const;
 
     virtual const sf::RectangleShape& getShape() const;
@@ -84,7 +85,6 @@ private:
     /// Used with rules : last to update has priority
     pro_maat::GridPos nextTarget;
 
-    template<State targetState, EntityType targetType>
     friend class Rule;
 };