Update CC: Tweaked to 1.13

Look, I originally had this split into several commits, but lots of
other cleanups got mixed in. I then backported some of the cleanups to
1.12, did other tidy ups there, and eventually the web of merges was
unreadable.

Yes, this is a horrible mess, but it's still nicer than it was. Anyway,
changes:

 - Flatten everything. For instance, there are now three instances of
   BlockComputer, two BlockTurtle, ItemPocketComputer. There's also no
   more BlockPeripheral (thank heavens) - there's separate block classes
   for each peripheral type.

 - Remove pretty much all legacy code. As we're breaking world
   compatibility anyway, we can remove all the code to load worlds from
   1.4 days.
 - The command system is largely rewriten to take advantage of 1.13's
   new system. It's very fancy!

 - WidgetTerminal now uses Minecraft's "GUI listener" system.

 - BREAKING CHANGE: All the codes in keys.lua are different, due to the
   move to LWJGL 3. Hopefully this won't have too much of an impact.

   I don't want to map to the old key codes on the Java side, as there
   always ends up being small but slight inconsistencies. IMO it's
   better to make a clean break - people should be using keys rather
   than hard coding the constants anyway.

 - commands.list now allows fetching sub-commands. The ROM has already
   been updated to allow fancy usage such as commands.time.set("noon").

 - Turtles, modems and cables can be waterlogged.

src/main/java/dan200/computercraft/api/pocket/AbstractPocketUpgrade.java

@@ -7,7 +7,9 @@
 package dan200.computercraft.api.pocket;
 
 import net.minecraft.item.ItemStack;
+import net.minecraft.util.IItemProvider;
 import net.minecraft.util.ResourceLocation;
+import net.minecraft.util.Util;
 
 import javax.annotation.Nonnull;
 
@@ -29,9 +31,14 @@ public abstract class AbstractPocketUpgrade implements IPocketUpgrade
         this.stack = stack;
     }
 
-    protected AbstractPocketUpgrade( ResourceLocation id, ItemStack stack )
+    protected AbstractPocketUpgrade( ResourceLocation id, String adjective, IItemProvider item )
     {
-        this( id, "upgrade." + id + ".adjective", stack );
+        this( id, adjective, new ItemStack( item ) );
+    }
+
+    protected AbstractPocketUpgrade( ResourceLocation id, IItemProvider item )
+    {
+        this( id, Util.makeTranslationKey( "upgrade", id ) + ".adjective", new ItemStack( item ) );
     }
 
     @Nonnull