Fluid cleanup and performance improvements (#3581)

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

src/main/java/appeng/client/me/InternalFluidSlotME.java

@@ -19,8 +19,6 @@
 package appeng.client.me;
 
 
-import net.minecraftforge.fluids.FluidStack;
-
 import appeng.api.storage.data.IAEFluidStack;
 
 
@@ -45,11 +43,6 @@ public class InternalFluidSlotME
 		this.yPos = displayY;
 	}
 
-	FluidStack getStack()
-	{
-		return this.getAEStack() == null ? null : this.getAEStack().getFluidStack();
-	}
-
 	IAEFluidStack getAEStack()
 	{
 		return this.repo.getReferenceFluid( this.offset );