QTKit not available anymore on macOS Sierra

[jfsantos]

This package does not compile anymore on Sierra as Apple has removed QTKit (see this issue from OpenCV for more info). OpenCV solved this by porting their code to use AVFoundation instead, but I have no experience with this so I'm just reporting this without a PR (sorry!).

[jdonald]

The first steps are fixing up camera.{h,m} are to #include <AVFoundation/AVFoundation.h> and handle some name-changes by replacing instances of QT with AV. Then there are other differences in the framework like QTCaptureDecompressedVideoOutput is now AVCaptureVideoDataOutput.

Then it's clear some of the delegate method signatures have changed in nontrivial ways, and this is certainly more than a 2-minute task and I stopped there.