Fluid cleanup and performance improvements (#3581)

Use custom gui widget with custom synchronization for rendering fake fluid slots.

src/main/java/appeng/fluids/items/BasicFluidStorageCell.java

@@ -27,7 +27,7 @@ import appeng.api.AEApi;
 import appeng.api.storage.IStorageChannel;
 import appeng.api.storage.channels.IFluidStorageChannel;
 import appeng.api.storage.data.IAEFluidStack;
-import appeng.fluids.contents.FluidCellConfig;
+import appeng.fluids.helper.FluidCellConfig;
 import appeng.items.materials.MaterialType;
 import appeng.items.storage.AbstractStorageCell;
 import appeng.util.InventoryAdaptor;

src/main/java/appeng/fluids/items/FluidDummyItem.java

@@ -78,6 +78,6 @@ public class FluidDummyItem extends AEBaseItem
 	@Override
 	protected void getCheckedSubItems( final CreativeTabs creativeTab, final NonNullList<ItemStack> itemStacks )
 	{
-		//Don't show this item in CreativeTabs
+		// Don't show this item in CreativeTabs
 	}
 }