re-publicize InstancedGeometry no-arg constructor, correct erroneous javadoc (#1230)

* re-publicize 3 no-arg constructors, correct/remove erroneous javadoc

* re-protect 2 no-arg constructors, restore javadoc

jme3-core/src/main/java/com/jme3/scene/Geometry.java

@@ -98,7 +98,8 @@ public class Geometry extends Spatial {
     private int nbSimultaneousGPUMorph = -1;
 
     /**
-     * Serialization only. Do not use.
+     * Instantiate a <code>Geometry</code> with no name, no mesh, and no
+     * material. The mesh and material must be set prior to rendering.
      */
     public Geometry() {
         this(null);

jme3-core/src/main/java/com/jme3/scene/Node.java

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2009-2018 jMonkeyEngine
+ * Copyright (c) 2009-2019 jMonkeyEngine
  * All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
@@ -83,7 +83,7 @@ public class Node extends Spatial {
     private boolean updateListValid = false;
 
     /**
-     * Serialization only. Do not use.
+     * Instantiate a <code>Node</code> with no name, no parent, and no children.
      */
     public Node() {
         this(null);
@@ -93,8 +93,7 @@ public class Node extends Spatial {
      * Constructor instantiates a new <code>Node</code> with a default empty
      * list for containing children.
      *
-     * @param name the name of the scene element. This is required for
+     * @param name the name of the scene element
-     * identification and comparison purposes.
      */
     public Node(String name) {
         super(name);

jme3-core/src/main/java/com/jme3/scene/instancing/InstancedGeometry.java

@@ -64,10 +64,7 @@ public class InstancedGeometry extends Geometry {
 
     private int firstUnusedIndex = 0;
 
-    /**
+    public InstancedGeometry() {
-     * Serialization only. Do not use.
-     */
-    protected InstancedGeometry() {
         super();
         setIgnoreTransform(true);
         setBatchHint(BatchHint.Never);