feat(examples/pachyderm-cd4ml): Add demo of redeploying old model

[philwinder]

What this PR does / why we need it:
Extended the pachyderm CD4ML example to include a demo of deploying an old versioned model.

This is really cool because you can be 100% sure that the old model is exactly the same as what you previously had production. This isn't always the case, depending on how you're doing your deployments.

Does this PR introduce a user-facing change?:

NONE

[seldondev]

Hi @philwinder. Thanks for your PR.

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[RafalSkolasinski]

/approve

[RafalSkolasinski]

Nice one!

[seldondev]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: RafalSkolasinski

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