merged video and audio nodes into a single media node

They performed exactly the same function so I don't think we need the clutter.

Also bumped the project version, but old projects are automatically converted.

app/task/precache/precachetask.cpp

@@ -31,7 +31,7 @@ PreCacheTask::PreCacheTask(VideoStreamPtr footage, Sequence* sequence) :
   viewer()->set_video_params(sequence->video_params());
   viewer()->set_audio_params(sequence->audio_params());
 
-  video_node_ = new VideoInput();
+  video_node_ = new MediaInput();
   video_node_->SetStream(footage);
 
   NodeParam::ConnectEdge(video_node_->output(), viewer()->texture_input());