Simplify media i/o interfaces

Completely revamped the entire media i/o data and handlers.  The
original idea was to have a system that would have connecting media
inputs and outputs, but at a certain point I realized that this was an
unnecessary complexity for what we wanted to do.  (Also, it reminded me
of directshow filters, and I HATE directshow with a passion, and
wouldn't wish it upon my greatest enemy)

Now, audio/video outputs are connected to directly, with better callback
handlers, and will eventually have the ability to automatically handle
conversions such as 4:4:4 to 4:2:0 when connecting to an input that uses
them.  Doing this will allow the video/audio i/o handlers to also
prevent duplicate conversion, as well as make it easier/simple to use.

My true goal for this is to make output and encoder plugins as simple to
create as possible.  I want to be able to be able to create an output
plugin with almost no real hassle of having to worry about image
conversions, media inputs/outputs, etc.  A plugin developer shouldn't
have to handle that sort of stuff when he/she doesn't really need to.

Plugins will be able to simply create a callback via obs_video() and/or
obs_audio(), and they will automatically receive the audio/video data in
the formats requested via a simple callback, without needing to do
almost anything else at all.

libobs/obs-data.h

@@ -22,7 +22,6 @@
 
 #include "graphics/graphics.h"
 
-#include "media-io/media-io.h"
 #include "media-io/video-io.h"
 #include "media-io/audio-io.h"
 
@@ -86,8 +85,6 @@ struct obs_subsystem {
 	DARRAY(struct output_info)  output_types;
 	DARRAY(struct service_info) service_types;
 
-	media_t                     media;
-
 	signal_handler_t            signals;
 	proc_handler_t              procs;