implemented value node

Also implements changes necessary to support an input data type
that changes. Much of that foundation was built in
`nodearchchanges`, but hadn't been finalized. This commit
finalizes and provides a reference implementation/test with the
"Value" node.

Fixes #1443

app/node/input/multicam/multicamnode.h

@@ -0,0 +1,11 @@
+#ifndef MULTICAMNODE_H
+#define MULTICAMNODE_H
+
+
+class MultiCamNode
+{
+public:
+  MultiCamNode();
+};
+
+#endif // MULTICAMNODE_H