Rework tags

Author: ImMorpheus

src/main/java/org/spongepowered/api/registry/Registry.java

@@ -25,10 +25,12 @@
 package org.spongepowered.api.registry;
 
 import org.spongepowered.api.ResourceKey;
+import org.spongepowered.api.tag.Tag;
 import org.spongepowered.api.util.annotation.DoNotStore;
 
 import java.util.Objects;
 import java.util.Optional;
+import java.util.Set;
 import java.util.stream.Stream;
 
 /**
@@ -120,6 +122,8 @@ default <V extends T> Optional<V> findValue(final RegistryKey<T> key) {
      */
     <V extends T> V value(ResourceKey key);
 
+    <V extends T> Set<V> taggedValues(Tag<T> key);
+
     /**
      * {@link Registry#value(ResourceKey)}, provided for convenience when using {@link RegistryKey}.
      *

src/main/java/org/spongepowered/api/tag/Tag.java

@@ -48,21 +48,6 @@
  *     {@link BlockTypeTags#LOGS_THAT_BURN}</li>
  * </ul>
  */
-public interface Tag<T> extends DefaultedRegistryValue, ResourceKeyed {
-
-    /**
-     * Gets all values that are associated with this tag.
-     *
-     * @return All tag values
-     */
-    Collection<T> values();
-
-    /**
-     * Gets whether this tag contains the supplied value.
-     *
-     * @param value Value to check
-     * @return Whether the value is contained in this tag.
-     */
-    boolean contains(T value);
+public interface Tag<T> extends ResourceKeyed {
 
 }