Remove v1alpha3 version

[andreyvelich]

Blocked by: #1392.
I removed v1alpha3 version since we use the v1beta1 in Kubeflow manifests.
As well, I removed unused Go packages from Gopkg.toml.

For some reason, v1_time.py and v1_unstructured_unstructured.py is not generated for the v1beta1 SDK. @jinchihe I saw your comment here: #1252 (comment).
Do you know how we can include them to the SDK ?
Can we use Swagger Import Mappings for it ?

/assign @gaocegege @johnugeorge

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[andreyvelich]

I solved above problem by modifying swagger_config.json with this:

 "typeMappings": {
    "V1Time": "datetime",
    "V1UnstructuredUnstructured": "dict()"
  }

I checked our Notebook example and it is working.
What do you think @jinchihe ?
I believe Kubernetes Python client follows the same way for the date:

https://github.com/kubernetes-client/python/blob/master/kubernetes/client/models/apps_v1beta1_deployment_condition.py#L36-L37

[andreyvelich]

After some tests, I think it's better to use object type instead of dict() for the unstructured. "V1UnstructuredUnstructured": "object".
K8s Python lib also follows this type for some attributes, for example here.

In that case, we can use deserialize method to convert object from the dict to Katib model.
I think, we should modify our API to return Katib model objects instead of simple dict so user can easily manipulate them.
What do you think @gaocegege @johnugeorge @jinchihe ?

As well, it is useful in KFP Katib launcher. We can use default mechanism of serialisation de-serialisation instead of writing our own function, like I did here: https://github.com/kubeflow/pipelines/blob/7f101c5e41f1e9cef02e6a94225e97815fc2327f/components/kubeflow/katib-launcher/src/launch_experiment.py#L63-L193.

[johnugeorge]

/lgtm