Some further cleanup and 1.13 cherry-picks

Are most of these changes small and petty? Yes. However, IMO they do
make the code more readable. Anyway, a summary of some of the more
interesting changes:

 - Expose Abstract*Upgrade classes in the API
 - Fix the spelling of Jonathan in the API docs (*shakes fist*)
 - Fix bug with printout not working in the offhand.
 - Rename any argments/variables accidentally named "m_*", and add an
   inspection to prevent it happening again.
 - Remove most of the Block*.Properties classes - just inline them in
   the parent class.
 - Return super.writeToNBT instead of reassigning at the top.

src/main/java/dan200/computercraft/shared/common/ColourableRecipe.java

@@ -78,11 +78,7 @@ public class ColourableRecipe extends IForgeRegistryEntry.Impl<IRecipe> implemen
             }
         }
 
-        if( colourable.isEmpty() )
-        {
-            return ItemStack.EMPTY;
-        }
-
+        if( colourable.isEmpty() ) return ItemStack.EMPTY;
         return ((IColouredItem) colourable.getItem()).withColour( colourable, tracker.getColour() );
     }