Rename kube app manager

[ant31]

• renamed instances of 'manager' to 'kube-app-manager' (fixes Rename 'manager' to a more specific name: kube-app-manager #173)
• Fixed selector on the prometheus ServiceMonitor (kustomize configuration)
• Generate a ready to use resource with make generate-resources:
  quickstart for new-user becomes: kubectl apply -f deploy/kube-app-manager-aio.yaml
  (related to Release images and resources #166)
• Grouped all the webhook configuration together, to simplify the main kustomization.yaml file

let me know if you'd prefer it to be cut in multiple PR.

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[ant31]

closed and splitted in 3 different commits/PR (#179, #178, #177)