Remove temp todo comments left in as reminders

These are no longer needed as there are now nodes which demonstrate what
each of these should be like.
DEG_get_typeinfo() -> DEG_get_node_typeinfo()
Typeinfo defines for node types
Draft "add_to_graph()" method for groups

NOTE: this probably won't work out as-is if we use the standard node
add methods, as there are no ID refs set yet when using that method...