Core and most of part 2

[ryanryantong]

Core features + AA, depth of field, refraction, direct lightning.

Still working on work efficient stream compaction with shared memory

[ryanryantong]

Final pull request for readmes. 2 late days used.

Note for grader:
I was unable to get stream compaction working for path tracer. I first did it on projects 2 code and after I passed all the test, it was already past 12am on my 2nd late day. I pushed my updated project 2 code for reference. I got the stream compaction code to run during the readme period and have included these updates here. However, there is still a bug with the stream compaction code that I cannot figure out (see debug statements in pathtrace.cu). I am hoping to get some partial credit for this part.