Added defines for list+number of all operation nodes to depsgraph

The purpose of these defines at toplevel is so that operations
over the nodes do not necessarily require setting up a full
aparatus for performing node traversal.

Also, the nodecount variable provides us with a valuable ability
to cross-check whether all nodes have been evaluated. (Then again,
it doesn't quite work, as not all nodes will be scheduled up)
Change operation type for rigidbody sim to special type for this purpose
Added dedicated "rebuild" operation type
Remove invalid comment
Merge branch 'WIP-GraphNodesList'

Conflicts:
	depsgraph/depsgraph_types.h