Rework AEItemStack (#3091)

* Use itemstack as itemdef
* HIGH_TAG/LOW_TAG should be compared both directions
* Remove getTagCompound
* Make Itemlist implementation independent
* Cache item id for performance reasons
* Add preconditions to saveguard against external meddling
* Chache itemDamage
* Remove IAEStackSearchKey for now, rename getDisplayStack

src/main/java/appeng/util/ItemSorters.java

@@ -97,7 +97,7 @@ public class ItemSorters
 				return CONFIG_BASED_SORT_BY_NAME.compare( o1, o2 );
 			}
 
-			final int cmp = api.compareItems( o1.getItemStack(), o2.getItemStack() );
+			final int cmp = api.compareItems( o1.asItemStackRepresentation(), o2.asItemStackRepresentation() );
 
 			if( getDirection() == SortDir.ASCENDING )
 			{