Add include guards
Disable the use of EmberPagingSceneManager.

 - Remove EmberPagingSceneManager from the build
 - Create dummy implementations for the needed scene manager related classes.
 - Use Ogre default scene manager or OctreeSceneManager if loaded.
 - Comment out RaySceneQueries which depend on World Geometry being
   supported by the scene manager in AvatarTerrainCursor and
   ThirdPersonCameraMount
Rename ISceneManagerAdapter

 - ISceneManagerAdapter is responsible for managing terrain related
   data, therefore rename it to ITerrainAdapter.
Move main menu scene manager instantiation

 - Remove instantiation of scene manager for the main menu from
   OgreSetup.
 - Directly create it in EmberOgre instead.
 - Rename scene manager and camera objects in EmberOgre.

Fix formatting in Scene.cpp
Change terrain intersection testing.

- Introduce rayIntersects to ITerrainAdapter to let the terrain
  implementation decide how to check for ray collisions.
- Use rayIntersects instead of RaySceneQueries in AvatarTerrainCursor,
  MainCamera and ThirdPersonCameraMount.
- In MainCamera, a result for the RaySceneQuery is created manually if
  the ray intersects with the terrain so the listeners do not have to be
  changed.
Use ST_EXTERIOR_REAL_FAR to create scene manager
Pass ray by reference in ITerrainAdapter
Resolve some coding standard issues.
Add Ogre::Terrain and Ogre::Paging to build
Move IPageData from scene manager specific code.
Use Ogre::Terrain component with a constant height.

- Only basic support, no paging or data from Mercator yet.
- No Materials used yet, so far the terrain is a black surface.
- Move the dummy implementations to a separate directory(can be deleted
  later if unnecessary)
WIP: Start to integrate paging

This commit is not intended to stay like this.