Support non texture.sampler specified glTF file

Examples: Clean up

Remove unnecessary "#include <specularmap_fragment>" from meshphysical_frag.glsl

Removed deprecated animation entities

Revert closure optimisations

Add MeshStandardMaterialSG

Updated Draco decoder javascript to the latest version.

Moved all Draco related stuff into a separate sub-folder that seems to
be a more common practice when it comes to multi file loaders. We can
keep it as it was if preferred.

We are also going to includ WebAssembly decoder in a separate PR.

Fix typo

MeshPhongMaterial: remove support for RectAreaLight

Recreated keyframe example: The same functionality, but only 7% animation code

RectAreaLightHelper: Removed unused variables

RectAreaLight: cleanup and refactoring

This reverts commit b0c0e3c7.

This reverts commit 5f2187fb.

This reverts commit d5b9bc68.

This reverts commit c60105d9.

This reverts commit 563060ae.

This reverts commit bece17cc.

This reverts commit 2b46f628.