Fixes spot light angle encoding problem for FBX

FalloffAngle is now set directly in degrees as it is converted to radians in a later stage (inner and outer angle).
Fixes range calculation in case no attenuation is set

range is returned with a default high value. The used 0.0f value results in division through 0 error when calculating the range inverse value. Additionally we need a very high value here to mimic no light attenuation.