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/param.cpp

@@ -212,6 +212,8 @@ QByteArray NodeParam::ValueToBytes(const NodeParam::DataType &type, const QVaria
   case kString:
   case kBuffer:
   case kVector:
+  case kShaderJob:
+  case kSampleJob:
   case kAny:
     break;
   }