Replace ItemTag API with new API that also expands to Tiles and Entities

By: Bjarne Koll <LynxPlay101@gmail.com>

paper-api/src/main/java/org/bukkit/persistence/PersistentDataHolder.java

@@ -0,0 +1,23 @@
+package org.bukkit.persistence;
+
+import org.jetbrains.annotations.NotNull;
+
+/**
+ * The {@link PersistentDataHolder} interface defines an object that can store
+ * custom persistent meta data on it.
+ */
+public interface PersistentDataHolder {
+
+    /**
+     * Returns a custom tag container capable of storing tags on the object.
+     *
+     * Note that the tags stored on this container are all stored under their
+     * own custom namespace therefore modifying default tags using this
+     * {@link PersistentDataHolder} is impossible.
+     *
+     * @return the persistent metadata container
+     */
+    @NotNull
+    PersistentDataContainer getPersistentDataContainer();
+
+}