nodes: minor overhaul to functionality

The nodes now have more control over how their accelerated shaders/sample
functions are run, as well as how items are popped off the value tables.
This allows for various optimizations that we didn't have access to before.

app/node/input/media/media.cpp

@@ -57,7 +57,7 @@ void MediaInput::Retranslate()
 
 NodeValueTable MediaInput::Value(NodeValueDatabase &value) const
 {
-  NodeValueTable table;
+  NodeValueTable table = value.Merge();
 
   if (connected_footage_) {
     rational media_duration = Timecode::timestamp_to_time(connected_footage_->duration(),
@@ -66,12 +66,6 @@ NodeValueTable MediaInput::Value(NodeValueDatabase &value) const
     table.Push(NodeInput::kRational, QVariant::fromValue(media_duration), this, "length");
   }
 
-  // Push buffer to the top of the stack
-  NodeValue buffer = value[footage_input_].GetWithMeta(NodeParam::kBuffer);
-  if (buffer.type() != NodeParam::kNone) {
-    table.Push(buffer);
-  }
-
   return table;
 }