Some performance or memory optimizations

Replaced String concat in loops with StringBuilder (performance)
Replaced for with keySet + Map.get() through for with entrySet (perf)
Changed inner classes to static classes, mostly struct like (memory)

src/main/java/appeng/util/inv/WrapperChainedInventory.java

@@ -13,7 +13,7 @@ import net.minecraft.item.ItemStack;
 public class WrapperChainedInventory implements IInventory
 {
 
-	class InvOffset
+	static class InvOffset
 	{
 
 		int offset;