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.   



I assume you're referring to [this comment](https://github.com/kmsquire/VideoIO.jl/pull/47#issuecomment-60503523).  It would be better to create a separate Issue for that problem (if there isn't one), and/or a separate pull request with this fix.  

Doing so makes it much easier to find in the future (and it also doesn't have anything to do with AVOptions).  Again, let me know if I can help in this regard.