RFE: Promote Datadog Integration Service to the contrib repository

[oleg-nenashev]

As discussed at the community meetings, we would like to have the Datadog service a part of the Keptn LTS package, See KEP-86 for the full proposal keptn/enhancement-proposals#86

To do so, some changes are needed in the project

#105 (comment)

[vadasambar]

Confirm the intent for a long-term support with maintainers . Confirmed with <gh:user-mention login="vadasambar"></gh:user-mention>

I think we can mark this one as done

[vadasambar]

Keptn 0.20 does not seem to be released yet.