disambiguated whether NodeParam::parent() would return a Node* or a QObject*

Old code assumes that a NodeParam's parent will always be a Node. The function
has been separated off and tweaked in the event that this is not the case.

app/node/inputarray.cpp

@@ -0,0 +1,6 @@
+#include "inputarray.h"
+
+InputArray::InputArray()
+{
+
+}