Added link to online wiki fo controls.

src/docs/asciidoc/jme3/advanced/nifty_gui_java_interaction.adoc

@@ -352,3 +352,4 @@ You're done with the basic Nifty +++<abbr title="Graphical User Interface">GUI</
 
 *  <<jme3/advanced/nifty_gui_scenarios#, Nifty GUI Scenarios>>
 *  link:https://versaweb.dl.sourceforge.net/project/nifty-gui/nifty-gui/1.3.2/nifty-gui-the-manual-1.3.2.pdf[Nifty GUI - the Manual]
+*  link:https://github.com/nifty-gui/nifty-gui/wiki/Controls[Controls]