track cloudevents version

[ryandawsonuk]

We're using a message-dumper/event-display service in knative-eventing examples that only works with CE 0.2. Suggests we're using CE 0.2. This might be the version that works with knative-eventing 0.11.0, which is what we typically use and I think kubeflow has been using. Need check this it may limit which knative eventing versions we can work with.

I have seen Seldon logging work with broker and 1.6.0 of https://github.com/openshift-knative/serverless-operator/blob/509e232ff16b47684e2adb7e4ac3b2bbef74b40b/CHANGELOG.md but not sure what version of eventing that is using.

[ryandawsonuk]

Seems we are using V1 - https://github.com/SeldonIO/seldon-core/blob/master/executor/logger/worker.go#L75