'Object info' node should default to "self"

Currently the 'Object info' node is useless without an object as input. The proposal is that it should just refer to itself when there is no input present. This exposes the use of any object's own Location, Rotation and Scale data in its node tree.

This is mainly useful when sharing a Node tree across multiple different objects.

(A bonus would be an 'ID' output. Though not sure about the feasibility of this as apparently Object ID's are reassigned every time a .blend is opened.)