fix links

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

@@ -40,7 +40,7 @@ See also: xref:jme3/requirements.adoc[requirements].
 
 == Physics
 
-*  xref:jme3/advanced/physics.adoc[JBullet physics binding]
+*  xref:xref:physics/physics.adoc[Bullet physics binding]
 **  xref:jme3/advanced/walking_character.adoc[Physical characters]
 **  xref:jme3/advanced/hinges_and_joints.adoc[Physical joints and hinges]
 **  xref:jme3/advanced/vehicles.adoc[Ray-cast vehicle]

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

@@ -91,7 +91,7 @@ a|Use the xref:input/input_handling.adoc[inputManager] to configure your custom
 
 a|stateManager +
 getStateManager()
-a|You use the Application's state manager to activate xref:jme3/advanced/application_states.adoc[AppStates], such as xref:jme3/advanced/physics.adoc[Physics].
+a|You use the Application's state manager to activate xref:jme3/advanced/application_states.adoc[AppStates], such as xref:physics/physics.adoc[Physics].
 
 |===
 [cols="25,75", options="header"]

docs/modules/tutorials/pages/beginner/hello_physics.adoc

@@ -508,7 +508,7 @@ Using physics everywhere in a game sounds like a cool idea, but it is easily ove
 
 == Conclusion
 
-You have learned how to activate the jBullet PhysicsSpace in an application by adding a `BulletAppState`. You have created PhysicsControls for simple Shape-based Geometries (for more complex shapes, read up on xref:ROOT:jme3/advanced/physics.adoc[CollisionShapes]). You have learned that physical objects are not only attached to the rootNode, but also registered to the PhysicsSpace. You know that it makes a difference whether a physical object has a mass (dynamic) or not (static). You are aware that overusing physics has a huge performance impact.
+You have learned how to activate the jBullet PhysicsSpace in an application by adding a `BulletAppState`. You have created PhysicsControls for simple Shape-based Geometries (for more complex shapes, read up on xref:physics/physics.adoc[CollisionShapes]). You have learned that physical objects are not only attached to the rootNode, but also registered to the PhysicsSpace. You know that it makes a difference whether a physical object has a mass (dynamic) or not (static). You are aware that overusing physics has a huge performance impact.
 
 
 [TIP]

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

@@ -528,7 +528,7 @@ Use collision detection. The most common solution is to use jme's physics integr
 *Learn more:*
 
 * xref:beginner/hello_collision.adoc[Hello Collision]
-* xref:ROOT:jme3/advanced/physics.adoc[Physics]
+* xref:physics/physics.adoc[Physics]
 * link:https://github.com/jMonkeyEngine/jmonkeyengine/tree/master/jme3-bullet/src/common/java/com/jme3/bullet[com.jme3.bullet.]
 * CapsuleCollisionShape versus CompoundCollisionShape, CharacterControl versus RigidBodyControl.
 
@@ -540,7 +540,7 @@ Add physics controls to Spatials and give them spherical or cylindrical bounding
 *Learn more:*
 
 * xref:beginner/hello_physics.adoc[Hello Physics]
-* xref:ROOT:jme3/advanced/physics.adoc[Physics]
+* xref:physics/physics.adoc[Physics]
 * link:https://github.com/jMonkeyEngine/jmonkeyengine/tree/master/jme3-core/src/main/java/com/jme3/bounding[com.jme3.bounding.]
 * link:https://github.com/jMonkeyEngine/jmonkeyengine/tree/master/jme3-bullet/src/main/java/com/jme3/bullet/collision[com.jme3.bullet.collisions]
 * link:https://github.com/jMonkeyEngine/jmonkeyengine/blob/master/jme3-bullet/src/common/java/com/jme3/bullet/control/RigidBodyControl.java[com.jme3.bullet.control.RigidBodyControl.java]