Support lowercase 'ns' and 'ni' obj material tokens

Previously, the obj material parser would interpret all key tokens
starting with 'n' as 'newmtl' tokens. However, there are other tokens
that can start with 'n', namely 'ns' and 'ni' for material properties.
Make the parser robust to such cases, despite their canonical forms
being uppercase.

Resolves #410.
Merge pull request #413 from jdduke/fix_ns_obj_material

Support lowercase 'ns' and 'ni' obj material tokens
[FBX] fix default light intensity to 100
Add intensity field in light structure and separate from diffuse etc (do not premultipiy )
add CastShadows field for aiLight
add Range field in Lights
[FBX] Add fbx material unparsed properties as meta-properties