Add support for various gltf types - gltf (loose files), embedded and binary

[sbtron]

Some really great work here and was hoping to contribute back.

BabylonJS now supports loading glTF-Binary types thanks to @julien-moreau and @kickserve.
Thought it might be interesting to expand the test page to include various glTF sample types.
gltf and gltf-embedded are supported by all engines. gltf-binary so far is only supported by Cesium and now BabylonJS.

You can find an example page here - http://gltf-test.azurewebsites.net/

The PR includes

• Additional models for the different glTF types
• Updated with latest babylonjs and babylonJS.gltfLoader which supports gltf binary
• Some updates to the javascript to display additional types on the index page.

I might not be using the most efficient js to create the links to various model types. Please feel free to suggest any improvements.

[cx20]

@sbtron Many thanks!