[Bleeding] Cleaned up unsafe casts. Addresses BUKKIT-844

Removed internal collection leaks from PluginDescriptionFile
BREAKING: PluginDescriptionFile.getAuthors() now returns List instead of
ArrayList

Various places with unsafe generics, notably List<Object> getList() in
Configurations are now referenced as <?>. This is nonbreaking, but
sourcecode will need to be revised when compiled.

By: Wesley Wolfe <weswolf@aol.com>

paper-api/src/main/java/org/bukkit/potion/Potion.java

@@ -1,13 +1,14 @@
 package org.bukkit.potion;
 
 import java.util.Collection;
-import java.util.Collections;
 
 import org.apache.commons.lang.Validate;
 import org.bukkit.Material;
 import org.bukkit.entity.LivingEntity;
 import org.bukkit.inventory.ItemStack;
 
+import com.google.common.collect.ImmutableList;
+
 /**
  * Represents a minecraft potion
  */
@@ -170,9 +171,8 @@ public class Potion {
      * @see Potion#toDamageValue()
      * @return The effects that this potion applies
      */
-    @SuppressWarnings("unchecked")
     public Collection<PotionEffect> getEffects() {
-        if(type == null) return Collections.EMPTY_SET;
+        if (type == null) return ImmutableList.<PotionEffect>of();
         return getBrewer().getEffectsFromDamage(toDamageValue());
     }