Added support for specular shininess parameter

Added support for exporting of shininess parameter (strength of the specular color of material). It was not exported from an input model before.

Just one line of code changed + added some white space.

Proposed modification can be easily tested by comparing conversion of samples/cube.dae model to .g3dj before and after applying the pull request (fbx-conv cube.dae cube.g3dj)

Regards,
Jarek