Deprecate ogre loader

I would not remove the Ogre loader for now, as it has proven to be quite stable. However, at this point it is a very limited format that is not suitable for modern games, and its tooling is starting to deteriorate.

For this reason, we should deprecate it without planning its removal. In addition, we should convert all examples that currently rely on the Ogre loader for unrelated purposes, such as loading the basic test scene, to use glTF models or J3O models serialized from jMonkey.

PLAN

1. Convert all example models that use ogre to gltf (unless they are specifically showcasing the ogre loader)
2. Change the examples to use these new gltf converted models
3. Mark the ogre loader as @Deprecated