WIP: VideoIO with AVOptions v0.01 (compatible with ffmpeg 2.4.2)

AVOptions API
============
Maximiliano Suster
October 2014

AVOptions provides a generic system to get/set options for Devices, formats and Codecs.
It relies on AVOptions, AVDictionary and AVDeviceCapabilitiesQuery APIs.
AVOptions API is contained in src/avoptions.jl.

Currently the following functions in work:

       document_all_options
       print_options
       is_option
       set_default_options   
       set_option 
       get_option
       create_dictionary
       set_options_with_dictionary

Ongoing work:
The following functions depend on the DeviceCapabilitiesQuery API.  Some require the newly updated ffmpeg 2.4 libraries (>=AVUtil 53). 

      query_device_ranges,
      set_device_with_query,
      list_devices
      get_metadata 
      
Examples and documentation will be presented once completed.   



Would you mind

1. moving this to `examples`
2. creating a separate, small pull request with just this change, since it has nothing else to do with the main point of this PR

Smaller PRs are generally more appreciated than large PRs, especially when the functionality has nothing to do with the main point of the PR.  Smaller PRs are also easier to review and merge.  Large ones tend to be held up by small issues in one place or another.

As an aside, when creating new directories, it's best to respect the naming conventions already in place (lower case initial letter).