Added Registerable interface.

src/main/java/com/massivecraft/massivecore/PredictateIsRegistered.java

@@ -0,0 +1,22 @@
+package com.massivecraft.massivecore;
+
+public class PredictateIsRegistered implements Predictate<Registerable>
+{
+	// -------------------------------------------- //
+	// INSTANCE & CONSTRUCT
+	// -------------------------------------------- //
+	
+	private static PredictateIsRegistered i = new PredictateIsRegistered();
+	public static PredictateIsRegistered get() { return i; }
+	
+	// -------------------------------------------- //
+	// OVERRIDE
+	// -------------------------------------------- //
+
+	@Override
+	public boolean apply(Registerable registerable)
+	{
+		return registerable.isRegistered();
+	}
+	
+}

src/main/java/com/massivecraft/massivecore/Registerable.java

@@ -0,0 +1,6 @@
+package com.massivecraft.massivecore;
+
+public interface Registerable
+{
+	public boolean isRegistered();
+}