fix links

docs/modules/ROOT/pages/jme3/features.adoc

@@ -274,7 +274,7 @@ a|OGG Vorbis music and sounds
 
 == GUI / HUD
 
-*  xref:jme3/advanced/hud.adoc[Orthogonal (Billboard) node]
+*  xref:core:ui/hud.adoc[Orthogonal (Billboard) node]
 *  xref:jme3/advanced/nifty_gui.adoc[Nifty GUI integration]
 
 

docs/modules/core/pages/app/simpleapplication.adoc

@@ -145,7 +145,7 @@ a|Low-level and high-level rendering interface. Mostly used internally.
 
 a|guiViewPort +
 getGuiViewPort()
-a|The view object for the orthogonal +++<abbr title="Graphical User Interface">GUI</abbr>+++ view. Only used internally for xref:jme3/advanced/hud.adoc[HUD]s.
+a|The view object for the orthogonal +++<abbr title="Graphical User Interface">GUI</abbr>+++ view. Only used internally for xref:ui/hud.adoc[HUD]s.
 
 a|timer
 a|An internal update loop timer, don't use. See `tpf` in `simpleUpdate()` below to learn about timers.
@@ -177,7 +177,7 @@ a|The root node of the scene graph. Attach a xref:scene/spatial.adoc[Spatial] to
 
 a|guiNode +
 getGuiNode()
-a|Attach flat +++<abbr title="Graphical User Interface">GUI</abbr>+++ elements (such as xref:jme3/advanced/hud.adoc[HUD] images and text) to this orthogonal +++<abbr title="Graphical User Interface">GUI</abbr>+++ node to make them appear on the screen.
+a|Attach flat +++<abbr title="Graphical User Interface">GUI</abbr>+++ elements (such as xref:ui/hud.adoc[HUD] images and text) to this orthogonal +++<abbr title="Graphical User Interface">GUI</abbr>+++ node to make them appear on the screen.
 
 a|flyCam +
 getFlyByCamera()

docs/modules/tutorials/pages/concepts/faq.adoc

@@ -624,7 +624,7 @@ Attach text and pictures to the orthogonal `guiNode` to create a heads-up displa
 
 *Learn more:*
 
-* xref:ROOT:jme3/advanced/hud.adoc[HUD]
+* xref:core:ui/hud.adoc[HUD]
 * link:https://github.com/jMonkeyEngine/jmonkeyengine/tree/master/jme3-core/src/main/java/com/jme3/font[com.jme3.font.]
 * link:https://github.com/jMonkeyEngine/jmonkeyengine/blob/master/jme3-core/src/main/java/com/jme3/ui/Picture.java[com.jme3.ui.Picture] guiNode.attachChild()