Make Ecmascripten and Native Client implementation of Takeout

[bwhite]

The takeout algorithms are all in C++ but some of their dependencies (e.g., OpenCV) would be difficult to use in these environments. We could make a custom image loader for each of these as that is really the main blocker and then just support the compatible subset of each.

https://github.com/kripken/emscripten/wiki

https://code.google.com/p/nativeclient/

[bwhite]

Need to rip out OpenCV as it is too big of a dependency

• Option 1: Move image IO in models to libjpeg-turbo/libjpeg only, make a separate job that can convert from "anything-to-jpeg". libjpeg: libjpeg library problem in o1/o2 compile mode emscripten-core/emscripten#379
• Option 2: Use the browser's image IO and find a way to get that into the image_fromstring function calls.
• For minor image processing, copy from OpenCV and maintain in tree: cv::resize, cv::getRectSubPix, cv::cvtColor
• Some models won't be supported without significant effort: Brisk, Face Detect.
• GIST needs fftw3 to work, it isn't clear if this will be practical.
• msgpack: It isn't clear if this will be hard to incorporate as is. We may need to conditional compile with the header-only msgpack (https://code.google.com/p/msgpack-cpp-lite/)