Implement OpenCL Deshake Filter

The goal of this project is to write a solid, feature-complete, and reasonably performant implementation of the deshake video filter in OpenCL. This filter uses motion estimation to compensate for erratic camera movement and smooth out shaky footage.

Secondary goals to be pursued if time allows include the addition of interop between macOS's videotoolbox API and the OpenCL filters as well as ports of some of the other simple post-processing filters (such as delogo).