Allow any book to be placed in a bookshelf

- Modifies the bookshelf model and blockstate to choose a texture dynamically based on the book item
- Changes bookshelf slots to accept all books from wizardry and vanilla minecraft by default
- Adds a couple of hooks to allow addons to register their own book items and model textures
- Adds a config option to allow modpack makers to add more book items

src/main/java/electroblob/wizardry/registry/WizardryBlocks.java

@@ -96,6 +96,8 @@ public final class WizardryBlocks {
 	@SubscribeEvent
 	public static void register(RegistryEvent.Register<Block> event){
 
+		BlockBookshelf.initBookProperties();
+
 		IForgeRegistry<Block> registry = event.getRegistry();
 
 		registerBlock(registry, "arcane_workbench", 		new BlockArcaneWorkbench().setHardness(1.0F).setCreativeTab(WizardryTabs.WIZARDRY));