Expose avatar entity being deleted.
Show simple info when the avatar entity id deleted.

For now this is very simple; we probably want to take a closer look at
how the death of a character is handled in general. Some game modes
would probably want to avoid player entities to be deleted at all.
Properly check for size of vector.

This fixes a bug where Atlas objects would get contaminated, leading to
SmartPtr errors elsewhere.
Improve iteration speed in Model.

The most common operation in the Model class is iteration over the
submodels, particle systems and lights. To improve performance we'll
keep a vector of these instances and iterate over this.
Fix issue with uncontrolled pitching.

By using separate nodes for pitch and yaw we can avoid rotation issues.
Don't abort other picking listeners.

The functionality whereby one listener can abort the whole picking
session isn't completely thought out. In this case it made editing of
terrain areas cumbersome if anything else obstructed the area editing
spheres.
Better to just keep it internally to each listener.
Draw the editing spheres no top of everything.

Together with a material which ignores depth checks this makes the
spheres easier to interact with.
Check that the local socket is valid.
Use nullptr where suitable.
Simplify code through C++11 semantics.
Handle invalid files better.
Use Ogre 1.9

 - OverlaySystem is now a component, add to build and initialize it in OgreSetup
 - Scene Managers can retrieve the OverlaySystem from OgreSetup and
   register it with themselves to show overlays.
 - Add some implemented methods due to Ogre interface changes.
 - Purge includes of OgreProgressiveMesh since it was removed.
 - TODO: use QueuedProgressiveMeshGenerator from Ogre. Current state
   throws some cast exceptions in the background.
Fix Ogre macro usage for Ogre 1.9

Now it requires ';' after the macro.
Use Ogre's built-in Lod generator.
Fix rebase.
Fix LodDefinition Lua bindings
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