Revision should be annotated with configurationGeneration

[mattmoor]

From #444

metadata:
  labels:
    elafros.dev/configurationGeneration: ...  # generation of configuration that created this Revision

This should be set alongside the configuration name here.

[evankanderson]

Update: the configurationGeneration should probably be an annotation, rather than a label. It's not clear what the benefit of doing a label search for a configurationGeneration would be.

[johnugeorge]

/assign @johnugeorge