New directory structure

* Major updates to wrapper script, so that only minimal changes
  are needed after wrapping.
* Split ffmpeg and libav wrappers into src/ffmpeg and src/libav
* Basic support for libav 0.8, 0.9, 0.10, ffmpeg 2.2, 2.3
  (needs testing)
* Filled out basic functionality
  * Clean up/update av_capture.jl
  * Clean up tutorial01.jl slightly
  * Define av_pix_fmt_desc_get for libav 0.8
* Added utils/README about wrapping, archived old wrap scripts.
* Updated TODO.md, README.md, and added examples/playvid.jl
* After `include(joinpath(Pkg.dir("AV"),"src","init.jl"))`,
  any submodule (AVCodecs, AVDevice, SWScale, etc.) can be loaded
* And many more updates
Add sigatomic_begin/end around sws_scale.

* Testing whether or not this fixes some crashes
Fix av_pix_fmt_desc_get for libav 0.8
Added videoFramerate to AVCapture, misc fixes