cleanup part 1:
- removed indices class
- renamed mesh attributes accessors
- move animation writer save out of main writer
- GLTFConverterContext is now GLTFAsset
cleanup part 2: accessor is now a JSONObject
inheriting from JSONObject
- warnings removal
- removal of specific serialization methods
- more JSONObject inheritance
- clean up + appliers on JSONValue
cleaning up outputStream handling & preparing to move most asset write from writer to asset.
move most of the writing logic in asset
add dedicated place for OpenCOLLADA additions
remove support for webgl-loader
cleanup and simplify streams
print error messages
re-enable compression
fix skinning and protect profile + root
remove useless table and better naming for shader properties
cleaner animation save
cleanup skin save
fix skinning
do not pass asset by copy + work-around case where geometry isn't referred by any node.
add example of assetModifier (to flip V texcoord)
Merge pull request #246 from KhronosGroup/dev-5

Dev-5