Add support for conditions

[drewbutlerbb4]

Add support for condition resources: https://github.com/tektoncd/pipeline/blob/master/docs/conditions.md

A direct example in kfp: https://github.com/kubeflow/pipelines/blob/0.2.2/samples/core/condition/condition.py

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[drewbutlerbb4]

/assign @drewbutlerbb4

[animeshsingh]

/label compiler

[k8s-ci-robot]

@animeshsingh: The label(s) /label compiler cannot be applied. These labels are supported: api-review, community/discussion, community/maintenance, community/question, cuj/build-train-deploy, cuj/multi-user, platform/aws, platform/azure, platform/gcp, platform/minikube, platform/other, tide/merge-method-merge, tide/merge-method-rebase, tide/merge-method-squash

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/label compiler

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[drewbutlerbb4]

This issue will remain after #84 because conditions that receive parameters from task outputs still fail. Once this issue is fixed another PR will be made to reconcile.