BlockHandler initialisation is a constant expression (#4891)

* BlockHandler initialisation is a constant expression

If we can't make it all namespaces, this is the next best I guess.

+ Tag handlers constexpr, const as needed
+ Inherit constructors
* Privatise handler functions

* More constexpr

Co-authored-by: Alexander Harkness <me@bearbin.net>

src/Blocks/BlockWorkbench.h

@@ -16,14 +16,9 @@ class cBlockWorkbenchHandler:
 
 public:
 
-	cBlockWorkbenchHandler(BLOCKTYPE a_BlockType):
-		Super(a_BlockType)
-	{
-	}
-
-
-
+	using Super::Super;
 
+private:
 
 	virtual bool OnUse(
 		cChunkInterface & a_ChunkInterface,
@@ -32,7 +27,7 @@ public:
 		const Vector3i a_BlockPos,
 		eBlockFace a_BlockFace,
 		const Vector3i a_CursorPos
-	) override
+	) const override
 	{
 		a_Player.GetStatManager().AddValue(Statistic::InteractWithCraftingTable);
 
@@ -45,7 +40,7 @@ public:
 
 
 
-	virtual bool IsUseable(void) override
+	virtual bool IsUseable(void) const override
 	{
 		return true;
 	}
@@ -54,7 +49,7 @@ public:
 
 
 
-	virtual ColourID GetMapBaseColourID(NIBBLETYPE a_Meta) override
+	virtual ColourID GetMapBaseColourID(NIBBLETYPE a_Meta) const override
 	{
 		UNUSED(a_Meta);
 		return 13;