Fix unsigned integers not processed correctly

Fix Vertex indices are processed as normal signed int, vertex index is unsigned int.
Add Reader.readNativeUInt
Fix Vertex indices of Face are int, now long
Fix some Material member is processed wrongly

Through following property of shared toon flag is either toon texture index or shared toon texture index, it always processed as normal toon texture index. It might cause the reading problem when the size of texture index is more than 1.