Support multiple binary chunks

[javagl]

According to the specification, there may be multiple binary chunks in a binary glTF asset. The first one is supposed to be the main binary buffer data. Others are implementation-defined.

Right now, the classes like GltfAsset* usually store all the binary data as a single ByteBuffer binaryData. This has to be generalized to handle multiple chunks, like a List<ByteBuffer> binaryDataChunks.