This allows more consistency in the manner we include core headers,
where previously there would be a mix of absolute, relative and
include path-dependent includes.
Using `misc/scripts/fix_headers.py` on all Godot files.
Some missing header guards were added, and the header inclusion order
was fixed in the Bullet module.
-Added default environment editor setting
-Added environment created by default in new projects
-Removed default light and ambient from spatial editor, to make the editor more PBR compliant
