initContainers: Investigating initContainers to be used in the operator

[avisiedo]

Add a set of proof of concepts using initContainers to set up the environment before running the main container.

The details can be seen in the InitContainers.md document.

Some of them are not finished. The current in progress and pending paths will be handled in different branches to shrink the scope.

Any comment are welcomed.

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• A makefile is provided to use the different PoC quick and easy.
• Some make rules need DOCKER_IMAGE to be defined to a valid image.
• make container-push need to be logged in the repository where the image will be pushed.
• To reference the poc, use the APP environment variable; export APP=poc-05-a.yaml; make app-deploy get-info.
• The traces could be seen by oc logs pod/pod-id -c container-id.

[frasertweedale]

Thanks @avisiedo! Merging.