Graduate MPI Operator, MXNet Operator and XGBoost Operator to v1

[terrytangyuan]

This is part of the roadmap.

[issue-label-bot[bot]]

Issue-Label Bot is automatically applying the labels:

Label	Probability
feature	0.84

Please mark this comment with :thumbsup: or :thumbsdown: to give our bot feedback! Links: app homepage, dashboard and code for this bot.

[terrytangyuan]

Progress are being tracked in individual repos:

• MXNet Operator https://github.com/kubeflow/mxnet-operator/issues/66
• MPI Operator https://github.com/kubeflow/mpi-operator/issues/217
• XGBoost Operator https://github.com/kubeflow/xgboost-operator/issues/44

[richardsliu]

As a reference, these are the graduation criteria for TFJob 1.0: https://github.com/kubeflow/tf-operator/issues/1076

[terrytangyuan]

Also here are some good references on criteria, processes, and past exits: https://github.com/kubeflow/community/blob/master/guidelines/application_requirements.md#reference