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/api/AbstractTurtleUpgrade.java

@@ -0,0 +1,98 @@
+/*
+ * This file is part of ComputerCraft - http://www.computercraft.info
+ * Copyright Daniel Ratcliffe, 2011-2019. Do not distribute without permission.
+ * Send enquiries to dratcliffe@gmail.com
+ */
+
+package dan200.computercraft.api;
+
+import dan200.computercraft.api.turtle.ITurtleUpgrade;
+import dan200.computercraft.api.turtle.TurtleUpgradeType;
+import net.minecraft.block.Block;
+import net.minecraft.item.Item;
+import net.minecraft.item.ItemStack;
+import net.minecraft.util.ResourceLocation;
+
+import javax.annotation.Nonnull;
+
+/**
+ * A base class for {@link ITurtleUpgrade}s.
+ *
+ * One does not have to use this, but it does provide a convenient template.
+ */
+public abstract class AbstractTurtleUpgrade implements ITurtleUpgrade
+{
+    private final ResourceLocation id;
+    private final int legacyId;
+    private final TurtleUpgradeType type;
+    private final String adjective;
+    private final ItemStack stack;
+
+    protected AbstractTurtleUpgrade( ResourceLocation id, int legacyId, TurtleUpgradeType type, String adjective, ItemStack stack )
+    {
+        this.id = id;
+        this.legacyId = legacyId;
+        this.type = type;
+        this.adjective = adjective;
+        this.stack = stack;
+    }
+
+    protected AbstractTurtleUpgrade( ResourceLocation id, int legacyId, TurtleUpgradeType type, String adjective, Item item )
+    {
+        this( id, legacyId, type, adjective, new ItemStack( item ) );
+    }
+
+    protected AbstractTurtleUpgrade( ResourceLocation id, int legacyId, TurtleUpgradeType type, String adjective, Block block )
+    {
+        this( id, legacyId, type, adjective, new ItemStack( block ) );
+    }
+
+    protected AbstractTurtleUpgrade( ResourceLocation id, int legacyId, TurtleUpgradeType type, ItemStack stack )
+    {
+        this( id, legacyId, type, "upgrade." + id + ".adjective", stack );
+    }
+
+    protected AbstractTurtleUpgrade( ResourceLocation id, int legacyId, TurtleUpgradeType type, Item item )
+    {
+        this( id, legacyId, type, new ItemStack( item ) );
+    }
+
+    protected AbstractTurtleUpgrade( ResourceLocation id, int legacyId, TurtleUpgradeType type, Block block )
+    {
+        this( id, legacyId, type, new ItemStack( block ) );
+    }
+
+    @Nonnull
+    @Override
+    public final ResourceLocation getUpgradeID()
+    {
+        return id;
+    }
+
+    @Override
+    public final int getLegacyUpgradeID()
+    {
+        return legacyId;
+    }
+
+    @Nonnull
+    @Override
+    public final String getUnlocalisedAdjective()
+    {
+        return adjective;
+    }
+
+    @Nonnull
+    @Override
+    public final TurtleUpgradeType getType()
+    {
+        return type;
+    }
+
+    @Nonnull
+    @Override
+    public final ItemStack getCraftingItem()
+    {
+        return stack;
+    }
+}

src/main/java/dan200/computercraft/api/media/IMedia.java

@@ -46,7 +46,7 @@ public interface IMedia
 
     /**
      * If this disk represents an item with audio (like a record), get the readable name of the audio track. ie:
-     * "Jonathon Coulton - Still Alive"
+     * "Jonathan Coulton - Still Alive"
      *
      * @param stack The {@link ItemStack} to modify.
      * @return The name, or null if this item does not represent an item with audio.

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

@@ -0,0 +1,57 @@
+/*
+ * This file is part of ComputerCraft - http://www.computercraft.info
+ * Copyright Daniel Ratcliffe, 2011-2019. Do not distribute without permission.
+ * Send enquiries to dratcliffe@gmail.com
+ */
+
+package dan200.computercraft.api.pocket;
+
+import net.minecraft.item.ItemStack;
+import net.minecraft.util.ResourceLocation;
+
+import javax.annotation.Nonnull;
+
+/**
+ * A base class for {@link IPocketUpgrade}s.
+ *
+ * One does not have to use this, but it does provide a convenient template.
+ */
+public abstract class AbstractPocketUpgrade implements IPocketUpgrade
+{
+    private final ResourceLocation id;
+    private final String adjective;
+    private final ItemStack stack;
+
+    protected AbstractPocketUpgrade( ResourceLocation id, String adjective, ItemStack stack )
+    {
+        this.id = id;
+        this.adjective = adjective;
+        this.stack = stack;
+    }
+
+    protected AbstractPocketUpgrade( ResourceLocation id, ItemStack stack )
+    {
+        this( id, "upgrade." + id + ".adjective", stack );
+    }
+
+    @Nonnull
+    @Override
+    public final ResourceLocation getUpgradeID()
+    {
+        return id;
+    }
+
+    @Nonnull
+    @Override
+    public final String getUnlocalisedAdjective()
+    {
+        return adjective;
+    }
+
+    @Nonnull
+    @Override
+    public final ItemStack getCraftingItem()
+    {
+        return stack;
+    }
+}

src/main/java/dan200/computercraft/api/turtle/event/TurtleInventoryEvent.java

@@ -11,7 +11,6 @@ import net.minecraft.item.ItemStack;
 import net.minecraft.util.math.BlockPos;
 import net.minecraft.world.World;
 import net.minecraftforge.common.util.FakePlayer;
-import net.minecraftforge.fml.common.eventhandler.Cancelable;
 import net.minecraftforge.items.IItemHandler;
 
 import javax.annotation.Nonnull;
@@ -21,7 +20,6 @@ import java.util.Objects;
 /**
  * Fired when a turtle attempts to interact with an inventory.
  */
-@Cancelable
 public abstract class TurtleInventoryEvent extends TurtleBlockEvent
 {
     private final IItemHandler handler;