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.

obs/window-basic-main.cpp

@@ -262,7 +262,7 @@ bool OBSBasic::InitGraphics()
 bool OBSBasic::InitAudio()
 {
 	/* TODO: load audio settings from config */
-	struct audio_info ai;
+	struct audio_output_info ai;
 	ai.name = "test";
 	ai.samples_per_sec = 44100;
 	ai.format = AUDIO_FORMAT_16BIT;