add_intr!() macro for adding intrinsics to the Player

If needed, player can just be replaced by another arg to the macro so this works on every other entity - but right now the player is the only thing to gain/lose intrinsics.

src/saveload_system.rs

@@ -95,6 +95,7 @@ pub fn save_game(ecs: &mut World) {
             IdentifiedItem,
             InBackpack,
             InflictsDamage,
+            IntrinsicChanged,
             Intrinsics,
             Item,
             KnownSpells,
@@ -227,6 +228,7 @@ pub fn load_game(ecs: &mut World) {
             IdentifiedItem,
             InBackpack,
             InflictsDamage,
+            IntrinsicChanged,
             Intrinsics,
             Item,
             KnownSpells,