Nodes: move node registration to nodes module

The main goal here is to move towards more self contained node
definitions. Previously, one would have to change `blenkernel` to
add a new node which is not necessary anymore. There is no need
for all these register functions to "leak out" of the nodes module.

Differential Revision: https://developer.blender.org/D16612

source/blender/nodes/function/node_function_util.hh

@@ -15,10 +15,10 @@
 
 #include "BLT_translation.h"
 
-#include "NOD_function.h"
 #include "NOD_multi_function.hh"
 #include "NOD_socket_declarations.hh"
 
+#include "node_function_register.hh"
 #include "node_util.h"
 
 #include "FN_multi_function_builder.hh"