Spell HUD rewrite and retexturing:

- Replaces the old hardcoded drawing methods with a new json-based system with support for multiple inbuilt and resource pack-defined skins.
- Adds a config option for choosing the spell HUD skin, along with a custom config GUI screen allowing the user to select from a list of available skins with a preview of the currently selected skin.
- Replaces the HUD texture file with a spell_hud subfolder, containing all the necessary textures and json files for the 12 inbuilt skins.
- Adds a subtle sound effect and scroling animation when switching spells
- Reorganises the control event code into a single handler class and converts this class and the spell HUD class to static event handlers.
- Fixes the HUD position option which got broken in the previous spell HUD commit

src/main/java/electroblob/wizardry/client/SpellHUDSkinChooserEntry.java

@@ -0,0 +1,38 @@
+package electroblob.wizardry.client;
+
+import java.util.Map;
+import java.util.Map.Entry;
+import java.util.stream.Collectors;
+
+import electroblob.wizardry.client.gui.GuiSelectHUDSkin;
+import electroblob.wizardry.client.gui.GuiSpellDisplay;
+import net.minecraftforge.client.gui.ForgeGuiFactory.ForgeConfigGui.ModIDEntry;
+import net.minecraftforge.fml.client.config.GuiConfig;
+import net.minecraftforge.fml.client.config.GuiConfigEntries;
+import net.minecraftforge.fml.client.config.GuiConfigEntries.SelectValueEntry;
+import net.minecraftforge.fml.client.config.IConfigElement;
+
+/**
+ * Custom config GUI for spell HUD skin selection; displays a list of all the loaded skins and a preview of the currently
+ * selected skin. based off of {@link ModIDEntry} from Forge.
+ */
+public class SpellHUDSkinChooserEntry extends SelectValueEntry {
+	
+    public SpellHUDSkinChooserEntry(GuiConfig owningScreen, GuiConfigEntries owningEntryList, IConfigElement prop)
+    {
+        super(owningScreen, owningEntryList, prop, getSelectableValues());
+        if (this.selectableValues.size() == 0)
+            this.btnValue.enabled = false;
+    }
+
+    private static Map<Object, String> getSelectableValues(){
+    	return GuiSpellDisplay.getSkins().entrySet().stream().collect(Collectors.toMap(Entry::getKey,
+    			e -> e.getValue().getName()));
+    }
+    
+    @Override // Copied from superclass to use custom child screen GUI class
+    public void valueButtonPressed(int slotIndex){
+        mc.displayGuiScreen(new GuiSelectHUDSkin(this.owningScreen, configElement, slotIndex, selectableValues, currentValue, enabled()));
+    }
+
+}