First implementation of rules

TODO :
 - Fix target as getter (currently broken because of inheritance by rules)
 - Smart pointers for entity store ?

src/Entity.cpp

@@ -33,6 +33,9 @@ Entity::Entity(const pugi::xml_node& entityNode, sf::Texture* texture)
             entityNode.attribute("w").as_int(1),
             entityNode.attribute("h").as_int(1)) {}
 
+Entity::Entity() : Entity(0,0,EntityType::Citizen,nullptr,0,0)
+{}
+
 void Entity::move(Orientation orientation)
 {
     // TODO : Add speed ?