Add a cache for prisoners online only, this should help performance #26

The cache listens to a lot of events and custom events to ensure the
cache is up to date, this way we don't have to loop through all the
prisoners in a jail every single time they move or something but instead
just check the cache.

src/main/java/com/graywolf336/jail/beans/CachePrisoner.java

@@ -0,0 +1,28 @@
+package com.graywolf336.jail.beans;
+
+/**
+ * An object for storing online cached prisoners.
+ * 
+ * @author graywolf336
+ * @since 3.0.0
+ * @version 1.0.0
+ */
+public class CachePrisoner {
+	private Jail jail;
+	private Prisoner p;
+	
+	public CachePrisoner(Jail jail, Prisoner prisoner) {
+		this.jail = jail;
+		this.p = prisoner;
+	}
+	
+	/** Gets the Jail this cache is in. */
+	public Jail getJail() {
+		return this.jail;
+	}
+	
+	/** Gets the Prisoner in this cache. */
+	public Prisoner getPrisoner() {
+		return this.p;
+	}
+}