[plugins] director: stubs for cluster-on-demand feature.

Change-Id: Iaf478529200e3214a2d98ef6f615de693a0febdb
[plugins] director: minor clarification

Change-Id: I86afb5f727df18a627686c1c5d04431a96383eb0
ideas ...

Change-Id: I488152a3916320e8326e820f9dd897e486ec03bd
docs: minor fixes

Change-Id: I73d0099ab8d99374b87018ed58d2d29a29e43d9a
snap

Change-Id: Ia02f12ff77cc8f835c9072f0c1041771515df2ab