Provide cmd line options to specify input data path and output folder

[MrNeRF]

Here we are with the implementation. Your defaults should work. Anybody else can specify with -i the path to the training data json and with -o an ouput folder for the rendered images.

[MrNeRF]

I didn't want to introduce any dependencies so this is very lightweight implementation with the bare minimum. I basically run it with: ./NeRFRenderCore -i /home/user/Downloads/Lego/transforms.json -o /home/user/output/

[JamesPerlman]

Awesome! Thank you!