Changed copyright end year to 2020 in every reference "Copyright (c) 2006-XXXX, assimp team".
Changed copyright end year to 2020 in every reference "Copyright (c) 2006-XXXX, ASSIMP Development Team".
Changed copyright end year to 2020 in LICENCE.rtf.
Changed copyright end year in CMakeFiles.txt files and any other places referencing Assimp with a copyright start and end year.
Importing of lights according to glTF 2.0 extension KHR_lights_punctual https://github.com/KhronosGroup/glTF/tree/master/extensions/2.0/Khronos/KHR_lights_punctual
Since glTF lights are based on PBR they use different attenuation model than conventional lights supported by assimp. It is possible to use attenuation factors in assimp to describe inverse square law fallof. But the light structure does not provide means to save range property. Therefore I resorted to use of metadata. When range parameter is present, I put it into 'PBR_LightRange' metadata of light's node. Please, see comment in glTF2Importer file.
