Added getter and setter for LegacyApplication's speed (#986)

jme3-core/src/main/java/com/jme3/app/SimpleApplication.java

@@ -124,6 +124,23 @@ public abstract class SimpleApplication extends LegacyApplication {
         setSettings(settings);
         super.start();
     }
+        
+    /**
+     * Returns the applications speed.
+     *
+     * @return The speed of the application.
+     */
+    public float getSpeed() {
+        return speed;
+    }
+    
+    /**
+     * Changes the application speed. 0.0f prevents the application from updating.
+     * @param speed The speed to set.
+     */
+    public void setSpeed(float speed) {
+        this.speed = speed;
+    }
 
     /**
      * Retrieves flyCam