Adds code for loading and saving sign data

src/main/java/net/knarcraft/permissionsigns/PermissionSigns.java

@@ -22,6 +22,24 @@ public final class PermissionSigns extends JavaPlugin {
 
     private static final Queue<SignCreationRequest> signCreationRequests = new PriorityQueue<>();
     private static String pluginVersion;
+    private static PermissionSigns instance;
+
+    /**
+     * Instantiates the permission signs class
+     */
+    public PermissionSigns() {
+        super();
+        instance = this;
+    }
+
+    /**
+     * Gets an instance of this plugin
+     *
+     * @return <p>An instance of this plugin</p>
+     */
+    public static PermissionSigns getInstance() {
+        return instance;
+    }
 
     /**
      * Gets the version of this plugin